Logica Utens
Phyllis Chiasson

According to Peirce, formal reasoning (or logica docens) is comprised of the process of deliberately making certain types of inferences at certain stages of an inquiry. On the other hand, reasoning habits (logica utens) are the acritical, and thus, non-deliberate, application of instinctive habits for making inferences. Our logica utens allows us to perform the thinking that "our regular business requires us daily to do[1]." The first task here will be to address the nature and function of the "everyday" reasoning methods which Peirce refers to as "reasoning instincts" and "logica utens." To do this we will need to examine Peircešs meaning of certain terms, including: "habits," "instincts," logica utens and logica docens‹and then examine some specific assertions that Peirce made about what a logica utens can and cannot do (or be). The second task is demonstrate, by means of pragmatically derived ex-amples of a theoretical model of logica utens[2], that Peirce may have been incorrect about certain of the assumptions he made concerning the nature of a logica utens. The third task will be to discuss the advantages to having a theoretical model of logica utens both for the deliberate refinement of reasoning habits, and the consequent development of better formal rea-soning skills (logica docens).
Key words: logica utens, logica docens, habit, abduction, induction, deduction

Whenever we make an inference, we pass from certain considerations that are already known (or assumed) to be true, to another consideration that is separate from the previous ones, but which follows from them. Formal logic concerns itself with the forms and validity of deliberately constructed inferences. Rarely, however, do we follow the dictates of formal logic for making inferences–nor do we need to most of the time. The majority of inferences we make in our daily lives are best made by means of habit (instinctively). Our instinctive reasoning habits allow us to function smoothly and efficiently in the day-to-day world, without having to stop at each moment of a decision-making process and deliberately engage formal reasoning practices.

Suppose, for example, that Joe Smith wakens to find that the sky is gray and that it is raining. His inference that it is going to be a rainy day causes him to make a decision that he should dress in rain gear and take his umbrella along with him to work that day. Suppose, however, that by the time he is dressed, the sun has broken through, and the rain has stopped.

What Joe will do next depends upon the next inference he makes–and, as for every inference, that depends upon what he already knows (or assumes) to be true. If the month is February and he lives in Seattle (when rain is a nearly constant event), Joe is likely to infer that more rain will follow later in the day, thus deciding to remain in his rain gear and bring his umbrella along with him to work. If Joe lives in Southern Arizona (where February rains are rare), he may infer that the storm is over and that there will be no need for rain gear that day.

Our first task here will be to address the nature and function of such "everyday" reasoning methods which Peirce refers to as "reasoning instincts" and "logica utens." To do this we will need to examine Peirce’s meaning of certain terms, including: "habits," "instincts," logica utens and logica docens and then, address some specific assertions that Peirce made about what a logica utens can and cannot do (or be).

Secondly, this paper will demonstrate, by means of pragmatically derived examples of a theoretical model of logica utens [3], that Peirce may have been incorrect about some of the assumptions he made concerning the nature of a logica utens.

Finally, we will discuss the advantages to having such a theoretical model of logica utens for the refinement of one’s reasoning habits and the development of the deliberate skills of formal reasoning methods (logica docens) as well.



A) Habits

Peirce defines the term "habit" very broadly "without any implication as to the time or manner in which it took birth, so as to be equivalent to the corrected phrase ‘habit or disposition,’ that is, as some general principle working in a man’s nature to determine how he will act…." [4] Elsewhere he defines "habit" as "that upon which we are prepared to act," [5] and still elsewhere, as the "perfection of a fixed character, which would be marked by an entire absence of self-reproach."[6] "Belief," Peirce tells us, "is not a momentary mode of consciousness; it is a habit of mind essentially enduring for some time, and mostly (at least) unconscious…."[7] Thus, the term "habit" is, for Peirce, one that applies to anything that we do (or believe) without "thinking about" the rightness or wrongness of doing (or believing) it.

B) Instincts

Peirce also defines the term "instinct" very broadly, within his definition of the term "habit."

"If I may be allowed to use the word "habit," without any implication as to the time or manner in which it took birth, so as to be equivalent to the corrected phrase "habit or disposition," that is, as some general principle working in a man’s nature to determine how he will act, then an instinct, in a proper sense of the word, is an inherited habit, or in more accurate language, an inherited disposition. But, since it is difficult to make sure whether a habit is inherited or is due to infantile training or tradition, I shall ask leave to employ the word "instinct" to cover both cases…. I am willing to grant that it is probable that some of our judgements of rationality of the very simplest kind have at the bottom instincts in the above broad sense. I am inclined to think that even these have been so often furbished up and painted over by reflection upon the nature of things that they are, in mature life, mostly ordinary habits. [8]

In other words, though we clearly acquire many habits throughout our lives, there are sorts of habits (instincts) that form so early in life and seem so fundamental to the nature of human functioning that they appear to be "inherited," rather than the product of experience. These "instincts," however may be so "furbished up and painted over by reflection on the nature of things" (by those who are reflective, we might add) that they become, over the course of maturing, mostly ordinary habits. However, in order to avoid needless arguing over the distinction between "inherited" (or instinctive habits) and those "acquired" habits which function like instincts, Peirce wisely chose to include the possibility of either "nurture" or "nature" (experience or inheritance) as the originating source of apparently instinctive habits.

C) Reasoning Instincts

Our reasoning instincts provide the means by which we make many important decisions in life. According to Peirce: "It is really instinct that procures the bulk of our knowledge."[9] Most of the time our instinctively formed inferences work just fine–especially when we are encountering familiar events such as Joe faces in deciding what to wear to work on a rainy morning. However, according to Peirce, instinctively formed inferences can lead us astray when we are dealing with novel situations. Philosopher, K. T. Fann discussing Peirce’s theory of abductive inference quotes Peirce as follows:

In ordinary life everybody has a reasoning instinct or habits of reasoning by which he forms his opinions concerning many matters of great importance…. In fact, "It is really instinct that procures the bulk of our knowledge" (2.18). Peirce thinks that we not only have a reasoning instinct, but also an instinctive theory of reasoning, for every reasoner "has some general idea of what good reasoning is" (2.186). Such a theory of reasoning, antecedent to any systematic study of the subject, constitutes our logica utens, the acritical and implicit logic of the common man.

But man does not possess a full stock of instincts to meet all occasions, "and so is forced upon the adventurous business of reasoning. When one’s purpose lies in the line of novelty, invention, generalization, theory–in a word, improvement of the situation–…instinct and the rule of thumb manifestly cease to be applicable…"[10]

Peirce has presented us with two different problems in the above statements. The first is a question as to the nature of logica utens. Is logica utens "a reasoning instinct" or is it "an instinctive theory of reasoning–or is it both?" The second problem is whether Peirce is correct when he claims that "instinct and the rule of thumb" cease to applicable when "one’s purpose lies in the line of novelty, invention, generalization, theory–in a word, improvement of the situation."

D) Logica Utens

a. What Does the Concept of Logica Utens Include?

It is possible to interpret the statement from K. T. Fann in more than one way. Does Peirce mean for logica utens to only apply to "an instinctive theory of what constitutes good reasoning," as Fann appears to be saying? Or does Peirce mean for logica utens to refer to a "reasoning instinct" as well? The best case seems to be for the latter (and more inclusive) meaning of logica utens, if upon no other basis than Peirce’s own concept of "terminological ethics."

Peirce took the terms logica utens and logica docens from the scholastics of medieval times, who apparently appropriated the concepts from earlier Muslim scholars. The Latin term "utens" is a derivative of the Latin word "uti," which means to use. The scholastics applied the term "logica utens" in a broadly general way to cover every type of decision-making that was not "scholastic" or of the scholastic method of reasoning (i.e. trained according to the accepted norms of reasoning).

Thus, if we assume that Peirce followed his own rigorous requirements of adhering to terminological ethics, we know that he would not have used a term from somewhere else to describe something different than the originators of the term intended. Nor would he have developed a term of his own to apply to a concept that someone else developed. For this reason, we have to assume that both logica utens and logica docens mean exactly whatever they meant to the scholastics, from whom Peirce appropriated the terms.

With the above in mind, we are here using the term "logica utens" to mean an instinctive and untrained habit for making inferences–as well as whatever acritically derived belief (or theory) a person has concerning what constitutes good reasoning.

b. Is It True That Logica Utens Is Always Ineffective For Novel Situations?

The second problem to be found within Fann’s statement is whether Peirce is correct when he claims that "instinct and the rule of thumb" cease to applicable when "one’s purpose lies in the line of novelty, invention, generalization, theory–in a word, improvement of the situation." It seems as though Peirce is suggesting there that there is only one sort of reasoning instinct (logica utens), which all humans share equally. Yet we need only look around us to see the very different ways in which individuals make inferences as they solve the problems within their daily lives. Peirce gives the following example of reasoning by means of a mental diagram:

Somebody shakes a pair of dice in a dice box and asks me to guess whether his next throw will be doublets or not. Before replying I make a mental diagram of all possible throws, and relying on that, I reply that I guess the throw will not show doublets. This is unquestioningly a probable inference. In making it, the only thing I am conscious of relying upon is my mental diagram, as representing the probable course of experience…. [11]

Later in this same essay Peirce continued:

In more complicated cases, say for example, in that guess about the pair of dice, I believe that our natural judgements as to what is reasonable are due to thinking over, ordinarily in a more or less confused way, what would happen. We imagine cases, place mental diagrams before our mind’s eye, and multiply these cases until a habit is formed of expecting that always to turn out the case, which has been seen to be the result in all the diagrams. To appeal to such a habit is a very different thing from appealing to any immediate instinct of rationality. That the process of forming a habit of diagrams is often performed there is no room for doubt. It is perfectly open to consciousness. Why may not all our natural judgments as to what is good reasoning be founded on habits formed in some such ways? [12]

So, we are left with the question of whether there is more than one sort of reasoning instinct, and whether differing individuals might have differing logica utens. If the answer to either of these is "yes," then we are left with the obvious question: "Can there then be a "reasoning instinct" for which the habit is to engage in the process of exploring novelty, inventing, developing theories, etc.?"

In order to answer this question, we will first examine some of the fundamental issues of a multi-modal concept of logica utens. Then we will take a pragmatic approach of presenting different scenarios, based upon Dorothy Davis’ model of logica utens,[13] for illustrating differing approaches for resolving the same problem. These scenarios will support the possibility that: "Yes, there is more than one sort of reasoning instinct, and that differing individuals can have differing logica utens." We are going to further suppose that reasoning instincts are instinctive ways of making inferences, and that, although practically everyone uses inductive reasoning of one type or another for all sorts of everyday matters, induction is not the only form in which a logica utens can play out. We will suppose that some individuals also instinctively use deduction and/or abduction as well.

A) A Multi-modal Theory of Logica Utens
Just as in formal logic, for which the reasoning process is comprised of differing types of inference, so too our instinctive reasoning habits are comprised of a type (or types) of inferencing method(s). However, unlike formal logic, for which we deliberately apply different types of inference for differing purposes, the inferencing habits of a logica utens, lack such deliberateness in their application because they are instinctively (or automatically) utilized. Thus, a logica utens, since it is taken as an instinctive (therefore non-deliberate) basis of action, fits with Peirce’s definition as "a ‘habit or disposition’–that is, "as some general principle working in a man’s nature to determine how he will act…." [14]

As mentioned earlier, when we make an inference (deliberate or not), we pass from considerations that are already known (or assumed) to be true, to a consideration separate from the previous ones, but which follows from them. Thus, in our example of Joe confronting a rainy morning, his prior considerations will have to do with his past experiences with rainy mornings for the context (in this case–time of year and location) in which he makes his inference.

Most of the time, we make inferences instinctively, allowing us to function smoothly in the day-to-day world. According to Peirce, this is how it should be. "The best plan…, on the whole," he wrote, "is to base our conduct as much as possible on instinct, but when we do reason to reason with severely scientific logic." [15]

B). Deliberate versus Non-deliberate Reasoning

Peirce applied the paired medieval terms of "logica utens" and "logica docens" to establish the difference between the non-deliberate nature of our instinctive reasoning habits and the deliberate choices of thought that are (or should be) made during scientific reasoning. (He includes the performing of experiments as thinking, "so that an experiment shall be an operation of thought."[16]) For Peirce then, deliberate reasoning is a species of conduct–which places thinking into the realm of ethics, and as such makes deliberate reasoning subject to praise or blame for the way in which the thinking is performed. Instinctive reasoning habits, on the other hand, are not subject to criticism, says Peirce, since "it is idle to criticize as good or bad that which cannot be controlled." [17]

In his system of formal logical methods, Peirce identified the standards and the order by which the three forms of inference should be performed: abduction (for the discovery and development of a hypothesis); deduction (for the explication and demonstration of the hypothesis); and induction (for the testing and evaluation of the hypothesis). Abduction is inference from a surprising fact to a possible explanation for that fact. Deduction is inference from premise to conclusion. Induction is inference from example to enumeration or generalization.

Peirce made it clear that his version of pragmatism (pragmaticism) is a theory of the deliberate conduct of reasoning (logica docens) and is, thus, not meant to explicate the instinctive reasoning habits of logica utens. He even claimed that logica utens, since it is non-deliberate, cannot properly be called reasoning at all.

A mental operation which is similar to reasoning in every other respect except that it is performed unconsciously cannot be called "reasoning’ (2.182) because "it is idle to criticize as good or bad that which cannot be controlled" (5.108). Since reasoning is a kind of voluntary and deliberate conduct, we are held responsible for its consequences. It is clear such conduct comes under the domain of ethics for ethics is the theory of self-controlled or deliberate conduct. [18]

Peirce also believed that, just as people hold tenaciously to any acritically indubitable (patently evident) belief, they tend to hold onto their acritically derived idea (or belief) of what constitutes good reasoning as well. The less knowledgeable people are about the standards of "good reasoning," the more likely they may be to maintain a tenacious hold on their "idea of good reasoning"–regardless of how ludicrous or illogical the methods and consequences such reasoning might be. [19, 20] In an 1892 lecture Peirce said:

It is wonderful how many people are to be met with who know nothing about reasoning. The popular opinion seems to be that if you find any similar relationship between things, and then find a supposed condition from which this relationship would certainly result, you have there some evidence that that condition really exists.[21]

What Peirce describes above is a method for making faulty inferences–inferences of the sort that are sometimes called "jumping to conclusions," and other times, "rushing to judgment." Everyone makes faulty inferences at one time or another; such is the nature of human minds. However, some people habitually make inferences in the way Peirce just described. The logica utens (or reasoning instinct) for these people causes them to habitually substitute a "guess" based upon simple similarities for "evidence," leading into a conclusion. On the other hand, some highly flexible people prefer making "guesses" based upon acritical intuitions about simple differences.[22] For these sorts of individuals "reasoning" is a series of instinctive acritical "intuitions," leading away from a topic, but not into any conclusions, or hypotheses. Unlike those who rely upon similarities as their basis for reasoning, however, these latter sorts of instinctive reasoners are more than happy to release one intuition (usually what Peirce termed an "accidental prepossession"[23]) when something new comes along. Peirce’s comment about poor reasoning refers to both of these types of acritical reasoners. Peirce tells us that such people "know nothing about reasoning." Yet it might just as easily be true that some of these people know a good deal "about" reasoning, but that their logica utens is such that their mental habit is to reason in the way he described above.[24]

What are the problems that come from making inferences by substituting a "guess" for "evidence," or by relying upon "acritical intuitions" about simple differences? Sometimes (perhaps most of the time if someone is living a simple life) no problem at all comes from operating in this way. Our "guesses," whether taken as "evidence" or "intuitions," may usually end up being correct (or else we never find out that we were incorrect–as when, say, others suffer the consequences of our mistaken "guess" after we are long gone from the situation).

All of us, regardless of the degree of reasoning complexity within our logica utens, sometimes reason in the ways described above. However, people who only know how to reason by means of substituting "guesses" for "evidence," or by means of "acritical intuitions," can end up creating problems for themselves, for others, and for situations in general. In other words, the "popular opinion" about reasoning, which Peirce described above, can easily lead any reasoner astray, but it will most often lead astray (especially in complex situations) those who have no access to other reasoning methods.

People who habitually reason in the way Peirce described above use one of two inferencing methods: "simple induction," or a form of transient abduction that might rightly be called "crude abduction." The meaning of "simple induction," as it pertains to logica utens, refers to a conclusive type of habitual reasoning based upon sorting by simple similarities. The logica utens of simple inductive reasoning refers to the habit of making inductively drawn conclusions based upon simple similarities and without reference to deduction or abduction. According to Peirce, induction is of two sorts: "crude" and "gradual" [25] This same division applies to induction when it is used as the sole method of a logica utens. [26] According to Peirce, "crude" inductive reasoning is the weakest form of argument, "liable to be demolished in a moment, as happened toward the end of the eighteenth century to the opinion of the scientific world that no stones fall from the sky[27]." The belief that "no stones (asteroids or meteors) fall from the sky" is an example of a conclusion based upon a belief due to "lack of evidence," rather than upon a "guess" taken as "evidence." The mental habit for applying gradual induction, "which makes a new estimate of the proportion of truth in the hypothesis with every new instance,[28]" provides the individual with this mental habit more openness to new information. However, both types of inductive reasoning habits are of a linear and "conclusive" nature. The main difference between them lies in the degree of tenacity with which a conclusion will be held. Both sorts of simple induction can move either from a "guess" taken as "evidence" for a conclusion, or from a "lack of evidence" taken as "evidence" (or proof) of a conclusion (as in "no stones fall from the sky").

On the other hand, the inference method that we might term "crude abduction" is applied by those who make their selections based upon variety (which can include "surprising facts") but who do not pull these selections together in meaningful ways[29]. The ephemeral nature of "crude abductive reasoning," which Peirce does not address in his theory of logica docens, makes it a transitory and unfocused mental habit, for which variety and change are the only guiding principles.

Simple induction and "crude" abduction are not, however, the only methods of a logica utens, although we all apply these instinctive methods at one time or another. Some individuals also instinctively employ "deductive reasoning" in tandem with the method Peirce terms "gradual induction" ("which makes a new estimate of the proportion of truth in the hypothesis with every new instance" [30]). Other individuals instinctively apply "abductive reasoning" in tandem with "gradual induction," without reference to deduction. Some people instinctively use a combination of instinctive reasoning skills, enabling them to apply any of these types of reasoning habits.

Thus, according to Davis’s Peirce-based model there are four basic modes of logica utens: 1) crude abduction (spontaneous, or transient reasoning); 2) simple induction (direct reasoning); 3) deduction paired with "gradual induction" (analytical reasoning); and 4) abduction paired with "gradual induction" (multi-relational, or abductive, reasoning). These instinctive modes for making inferences do not correspond directly to particular methods in Peirce’s logica docens–nor should they be expected to do so. Taken together, however, the modes of logica utens can be viewed as having an untrained, but analogous, relationship to Peirce’s concept of formal logical methods.

In Peirce’s logica docens, abduction (for the formation of a hypothesis) is the first stage of scientific inquiry. However, according to Peirce, abduction "does not afford security. The hypothesis must be tested." [31] However, when abductive inferences are used for non-scientific purposes (as for art or creative writing), the consequence of abductive reasoning can be the "end" of a process, with no further "testing" required. Abduction is the only inferencing method by which original ideas can be created or discovered (which is true whether the abduction occurs instinctually, as a logica utens, or deliberately, as logica docens). Some people seem to come equipped with a logica utens that gives them the ability to identify and pursue qualitative anomalies. Such individuals appear to be innately drawn to the unique and unusual, and able to apply "gradual induction" in tandem with abduction to discover and develop original ideas and hypotheses. Others must be deliberately taught how to identify the qualities of things so that, by means of deliberate practice, they can develop the ability to notice and address qualitative anomalies.

Deduction, says Peirce, has two parts: explication and demonstration. With deduction we plan and prepare for things. We figure out how to do something in advance of doing it, thinking through potential problems as much as is possible. Peirce says:

"[Deduction] invariably requires something in the nature of a diagram; that is an "Icon," or Sign that represents its Object in resembling it. It usually, too, needs "Indices," or Signs that represent their objects by being actually connected to them. But [deduction] is mainly composed of "Symbols," or Signs that represent their Objects essentially because they will be so interpreted." [32]

Thus, it is with the mental or physical tools of analysis that we think our way through problems deductively. Some people apparently come equipped with a logica utens that has provided them with such mental tools, allowing them to easily utilize mental diagrams and whatever else they need to perform effective deductive analyses. Others need to learn the tools of analysis, so that, by deliberately putting these into practice, they can begin to habituate them into their logica utens and become more effective reasoners.

Induction, the third stage of inquiry, can be of two sorts: "crude" and "gradual."

Crude induction[33] involves simple enumeration–collecting examples for pre-existing categories (or for verifying the "truth" of past beliefs and prior experience). When used as a logica utens, crude induction does not make room for open-mindedness. Much like the votes being tallied for one candidate or another, something is conclusively one thing or it is another–period. Thus, people who rely upon "crude induction" as their logica utens tend to be "either-or" and "black or white" sorts of thinkers.

Gradual induction [34], on the other hand, involves "making a new estimate of the proportion of truth in the hypothesis (or belief) with every new instance; and given any degree of error there will sometime be an estimate (or would be if the probation were persisted in) which will be the absolutely last to be infected with so much falsity." In other words, "gradual induction" involves (whether deliberately, or instinctively), keeping a relatively open mind to new information and, in the case of learning, to the mastery of skills by means of repetition–to the point of their "perfection" and habituation.

With this in mind, let us now explore each of the four basic logica utens mentioned earlier–1) crude abduction; 2) simple induction; 3) deduction; and 4) abduction–to see how each might play out for a given situation. [In Davis’s non-verbal model of logica utens these four reasoning habits are respectively termed 1) "Transient Thinking," 2) "Linear Thinking," 3) "Analytical Thinking," and 4) "Multi-relational Thinking."]

Suppose, as an example, that someone (let’s call him Ron) has a dog who wanders into the house dripping wet (a known consideration). Since his dog is usually dry (another known consideration), the dog’s wetness is a "simple (obvious) difference" from its usual state (a third and distinct consideration). This obvious difference is a "surprising event" for Ron. So, since he is attracted to variety, the wetness of his dog (an obvious qualitative change) catches his attention. Maybe Ron will then decide to dry the dog off. If so, since he does not look very far forward to consequences, nor backward to experience, Ron is likely to use whatever is available for drying his dog. Perhaps he will use the pristine white monogrammed towels in the downstairs bathroom; perhaps the hand crocheted wool throw that hangs over the edge of the couch; perhaps he will allow the dog roll to around on the carpet until dry. In any case, Ron will not invest much time in wondering how the dog got wet, or what to do about it–other than whatever simple option presents itself in the immediate present.

Ron is a type of "means-directed" thinker, which is to say that the qualities of things (rather than a goal, aim, or desired solution) will direct his choices. At the same time, he is also attracted more to differences (or variety) than he is to similarities–and he abhors repetition. Ron relies upon "crude" abduction which means that he is attracted to qualitative differences, but not to exploring the significance of these. For, as a rule, someone who reasons as Ron does is not interested in reasons or explanations for things or events. Whatever happens…happens, and (much like Camus’ character, Mersault, in L’Etrangér), Ron tends (or prefers) to experience the next anomalous opportunity by responding to it as a singular phenomenon.

Now suppose that it is James’s dog who wanders into the house dripping wet (a known consideration). James knows from experience that, when gardening, his wife likes to let the dog run free in the yard. If the sprinkler happens to running, the dog often runs through it and gets wet (another known consideration). There is a similarity between two known considerations (James’ wet dog and the sprinkler in the past + James’ wet dog now), so he feels that he has evidence (a third and distinct consideration) that his wife is working in the yard and currently has the sprinkler on. This latter assumption is based upon a "supposed condition" that would certainly cause his dog to be wet, which he takes as evidence of the cause of his dog’s present state.

However, James does not have evidence…he merely has a guess (in the form of an assumption based upon a crude inductive inference), which he is taking as evidence. Because James habitually employs crude inductive reasoning, he will quickly jump to a conclusion of some sort. It could very well be that the dog is wet due to some other water source–such as rolling around in James’ koi pond, or being hosed down by an irate neighbor for burrowing into her flowerbed.

Whether correct or not, James’s belief about the reason that his dog is wet is going to produce consequences in his behavior. If he concludes that his dog being wet is evidence that his wife is working in the yard and has the lawn sprinklers running, perhaps he will do nothing other than find a towel and dry him off. In that case, the effect of James’ belief upon what he does based on that belief (his conduct) may begin and end with getting the dog dried off. But toweling the dog dry may not be the sum total of the effects of James’ belief (about the cause of his dog’s wetness) on human conduct.

What if he’s wrong? Suppose his wife has not turned on the water. Suppose, instead that his wife (after failing to tightly latch the gate of the dog run) has gone across the street to visit with a neighbor, entirely unaware that the dog has been running loose. If James is the sort of person who mistakes a "guess" for "evidence," (and thus, does not habitually check things out to see if he is correct) he might easily end up with unexpected consequences. Perhaps he will eventually discover dead fish which the dog has flung outside of the koi pond (and which might have been saved had James found them in time). Or perhaps James will end up with a fuming neighbor who (by "jumping to conclusions" and making an inference in exactly the same way as James has done), feels that she now has "evidence" that James is an irresponsible dog owner. (Perhaps, because of her assumption, his neighbor begins acting coldly toward him for what seems to be no apparent reason).

Peirce tells us that the meaning of any proposition (in this case: "The dog is wet because the sprinklers are on") resides in the consequences that it produces on the conduct of human behavior. As you can imagine, if either the koi pond or the irate neighbor is the cause of James’ dog being wet, and his behavior is to merely towel the dog dry (and not to also check out what caused his wetness), he might encounter unexpected consequences. In any case, because the meaning of his proposition (or assertion) is based upon the consequences it has upon the behavior of human conduct (not just upon his own conduct), James’ "evidence" can produce consequences upon the conduct of others. Those consequences are part of the meaning of James’ "evidence," and may, indeed, prove his "evidence" wrong.

If James were to use the inductive logica utens of "gradual induction," he would maintain an open mind by evaluating each situation as it comes along. Although he is still likely to "hold his guesses for true," he will not hold them so tenaciously that no new learning is possible. Some people are able to use a purely inductive logica utens very effectively because they have the habit of performing gradual inductions based upon having sufficient training and well-founded experience, rather than the habit of "jumping to conclusions" that those who instinctively apply crude induction are wont to do. For the most part, those who habitually apply gradual induction have mastered the protocols (directions as to what to do and how to do it) for many different situations. (We do, however, encounter highly educated and well-trained individuals who never-the-less apply crude inductive reasoning, and poorly educated people who are capable of learning by means of gradual induction.) Thus, the difference between those who instinctively apply "crude" versus "gradual" induction may be a difference of personality rather than aptitude. In any case, instinctive inductive reasoners of any sort, who have good educational and training experiences will be more prepared to deal effectively with a variety of situations than those who have limited exposure to training opportunities, education, or enriched life experiences.

In addition to simple inductive and "crude" abductive inferences (which most of us use to one degree or another within our logica utens), some people instinctively apply deductive inferences as well. People who reason deductively tend to use "gradual induction" in tandem with deduction. As mentioned earlier, gradual induction "makes a new estimate of the proportion of truth in the hypothesis with every new instance."[35] Those who instinctively apply deduction and gradual induction are usually able to recognize the difference between "evidence" and a "guess." It is the habit of such people to determine whether a particular "guess" (or hypothesis) is likely to be correct or not before deciding what to do next.

Let’s suppose for example that the wet dog belongs to Raymond, who instinctively uses deduction as well as gradual induction as his logica utens. Raymond, may also towel the dog dry, but as he does so he may wonder about the way in which his dog got wet this time. Raymond knows that there are several ways his dog could have gotten wet this time, although he also knows that his wife often lets the dog out of the dog run and lets him play in the sprinkler as she is working in the yard. However, Raymond does not draw a conclusion at this point. Like James, he does not yet know for sure if his wife is working in the yard or if she has the sprinklers on. But, unlike James, he does not make an assumption (or "guess") that she must be gardening with the sprinklers on and take that as "evidence" for why the dog is wet. Instead, Raymond realizes that there could be other ways in which his dog got wet this time, and that not all of these ways would be as benign as running through the sprinkler.

Unlike those who instinctively use simple induction (mistaking a "guess" for "evidence," and not realizing that there could be potential consequences for failing to make an effective inference), Raymond is fully aware that there are alternative explanations as to why his dog is wet. He is also fully aware that there are potential consequences awaiting, depending upon how his dog got wet.

So, what would Raymond do next?

He would check to see if his wife is working in the yard and if so, is the sprinkler running? If his wife is not working in the yard, or if the sprinkler is not running, then Raymond knows he has additional checking to do. Yet, even if his wife is in the yard and the sprinkler is running, he knows that the dog could still have gotten wet in some other way. So, Raymond verifies his guess by asking his wife if she knows for sure whether the dog got wet running through the sprinkler. If so, Ray may decide to check the koi pond anyway, just to be safe.

If there is reason to believe that the dog might not have gotten wet in the sprinkler, he will begin to eliminate other possibilities–perhaps he will make sure that the garden gate is tightly shut. Perhaps he will check the perimeter of the fence to make sure the dog has not dug a hole under the fence into a neighbor’s yard. In other words, Raymond (because he instinctively uses deduction to analyze the possibilities in a situation and gradual induction for testing his analysis) is less likely to fall prey to inferential fallacies than someone who habitually relies upon crude induction alone.

A third type of logica utens is applied by those whose reasoning instinct leads them to habitually focus upon subtle qualitative anomalies. Habitual abductive reasoners apply abductive reasoning for the discovery and development of a hunch, or hypothesis–and gradual induction for "estimating the proportion of the truth in the hypothesis with every new instance…." [36] (Though many habitual abductive reasoners also possess deductive reasoning abilities, some do not. Those with a "purely abductive" logica utens rely only upon abduction and gradual induction for their "everyday" reasoning needs. They are "means directed" reasoners–which is to say that they are guided by the unfolding of qualities in the process of making relationships among things, rather than by a goal.[37])

Now, suppose Larry (whose habitual reasoning is instinctively guided by unfolding the qualities of things) owns the wet dog. As he is drying the dog off, Larry happens to notice what appears to be a fragment of a water lily root embedded in the fur of the dog’s ear. This is a "surprising fact" for Larry and causes him to wonder if his dog might have gotten into the koi pond. Larry reasoning works like this:

  • There is a fragment of thin root with several branchings embedded in the fur of my dog’s ear that has the qualities of a water lily root a fragment.
  • If my dog became wet by rolling around in the koi pond, then it would not be unusual for a water lily root fragment to become embedded in the fur of his ear.
  • Therefore, there is reason to suspect that my dog might have gotten wet by rolling around in the koi pond.

At this point, Larry knows that he has only made a "guess." Thus, his first task is to go to the koi pond and see if there are any signs that the koi pond has been disrupted in the way it would be if a dog had been rolling around in it. If there are such signs and the root fragment indeed matches a water lily root, then Larry may feel justified in assuming that his dog got wet by rolling in the koi pond. If signs of rolling around exist, but the fragment does not match a water lily root, Larry may suspect that his dog has been up to mischief elsewhere as well, and set out to find out where.

If there are no signs that the dog was rolling around in the koi pond, however, Larry will probably make a new guess as to the origin of that root fragment in the fur of his dog. He might think further about the qualities of that root fragment and what made him think it came from a water lily. Perhaps the fact that there was no dirt on the root caused him to mistakenly assume it was a water lily root. If so, Larry might wonder: "What else could cause a root with no dirt on it to become embedded in my dog’s fur?"

This process of forming, then testing, then revising or reforming guesses based upon selection and rejection among the subtle qualities of things is the modus operendi of the logica utens of a habitual abductive reasoner. However, there is an interesting consequence to this qualitative, means-directed reasoning process: rarely does an instinctive abductive reasoner such as Larry end up where you would suppose he might. The chances are good, that even if Larry never tracks down the actual source of the root fragment (the "means" which, in this case, began Larry’s search for a cause, or "end"), that root fragment will lead Larry in new directions.

As Larry begins his "wondering" about what might cause a root with no dirt on it to become embedded in his dog’s fir, he might also become interested in the shape of this root as it compares to the shape of other roots. Perhaps this wondering will lead him to a book on root shapes, or perhaps he will dig up a few different plants in his garden, wash off the roots, and inspect their shapes. By now, Larry’s interest in root forms has nothing to do with his dog–except that his original interest was sparked by the root fragment in the fur of his dog’s ear. As Larry makes relationships between different sorts of root shapes, that may cause him to wonder about something else–say the role of certain root shapes for drought resistance (leading him to explore the cause of weather patterns). Or, if Larry is an artist, this root could just as easily lead him to try using the root shapes as paint brushes by dipping various root shapes into paint and recreating these shapes on a canvas–even "creating" new patterns of relationships as he does this. Or, if Larry is businessman, he might begin thinking about the pattern of relationships within various root systems and how, taken together, they fuel a single plant. Such thoughts might lead Larry to thinking about new ways of creating relational patterns (such as in those root systems) within his corporation to replace the bottom down hierarchy that currently exists.

No one (not even the instinctive abductive reasoners themselves) can predict where a thought will lead. Such is the nature of means-directed thinking. Instinctive abductive reasoning moves from a "guess" (or tentative hypothesis) to "gradual induction" ("which makes a new estimate of the proportion of truth in the hypothesis with every new instance"[38]). People using this reasoning instinct maneuver back and forth between abduction and gradual induction, depending upon where the "means" lead them. In this way, instinctive abductive reasoners do not reach conclusions so much as they raise new questions. Habitual reasoning for people like Larry is directed by the qualities of a thing or idea. which are placed into juxtaposition with the qualities of another thing or idea, which then results in a new "possibility," rather than a conclusion. Larry and those who instinctively reason as he does are led by exploring possibilities, rather than by figuring something out once and for all.

Certain advantages arise from considering logica utens in the way we have done here. For, at present, little is known about how people "actually do reason" in contrast to how they "should" reason. Peirce did not seem to think that this lack of knowledge of a theory about the methods of logica utens is of much consequence:

In everyday business, reasoning is tolerably successful; but I am inclined to think that it is done as well without the aid of a theory as with it. A Logica Utens, like the analytical mechanics resident in the billiard player’s nerves, best fulfils familiar uses.[39]

However, although Peirce’s "inclination" that a theory of logica utens may not be necessary for its "performance," a theory of logica utens may be essential for understanding and mastering Peirce’s logica docens. For, as we examine the nature of these "non-deliberate" instinctive processes, it becomes apparent that certain instinctive habits of logica utens (especially abduction) can adequately fulfil novel purposes. For this reason if no other, a theory of logica utens is useful for identifying and transmitting to the general population all of the skills of Peirce’s logica docens.


A knowledge of your own "instinctive" reasoning habits can provide you with the information necessary for finding a good match between your innate mental habits and the way in which you best learn, work, and tackle problems and projects of all sorts. Such knowledge will also point to the ways in which you can begin to improve upon your innate reasoning abilities. "But in truth," Peirce tells us, " there is but one state of mind from which you can ‘set out’, namely, the very state of mind in which you actually find yourself when you do ‘set out’…."[40] Peirce was thinking of the "content" of thought when he wrote this. However, it is not difficult to see that an understanding of the instinctive method by which you "set out" to engage in a reasoning activity can be useful for analyzing your own reasoning process. You might also see that being able to compare and contrast your own instinctive reasoning habits with those that others use (as well as with the logica docens as Peirce proposed it) will be helpful for developing more effective reasoning skills. By deliberately developing new reasoning skills, you can, with deliberate practice, develop new habits of thought–which, once habituated, will become part of your logica utens.

This paper has identified basic reasoning instincts (or logica utens) that loosely correspond to the inferencing methods of Peirce’s logica docens. Our logica utens allows us to perform the thinking that "our regular business requires us daily to do." [41] Dorothy Davis’s non-verbal theoretical model of logica utens [42] demonstrates that these mental habits are non-deliberate mirrors of the inference methods of Peirce’s methodeutic. Because of the investigations made possible by Davis’s model, we can see that Peirce may have been incorrect about certain of the assumptions he made concerning the nature of a logica utens–including his statement that logica utens does not work well for addressing novel situations. Based upon Davis’s model and the observations made possible by the non-verbal assessment tool, it appears that abduction, at its root, may even be a form of the logica utens which certain people instinctively apply. In addition, we have countered Peirce’s inclination that a theory of logica utens is unnecessary. Quite to the contrary, there are distinct advantages to having a theoretical model of logica utens. Such a theory is especially useful for the identification of an individual’s instinctive mental habits, permitting that person to deliberately refine thinking processes and produce more effective reasoning skills. Such refinement will also effect the consequent development of better formal reasoning skills (logica docens).

First published: January, 2001
Content last modified: January, 2001