Psychologism, according to the Stanford Encyclopaedia of Philosophy, is a term used by authors to refer to “what they perceive as the mistake of identifying non-psychological with psychological entities,” (Kusch Preface). Frege uses the term, more specifically, to refer to the mistake of treating logic as a special branch of psychology. It is important to realize that the psychologistic viewpoint is no single argument, nor can it be effectively dismissed by refuting any one argument. Rather, the psychologistic viewpoint is several arguments brought together by common assumptions, each one bringing out the implications of a certain element in those assumptions. Over the course of this paper, we will examine the strongest arguments in favour of the psychologistic viewpoint and Frege’s response to each of these arguments. Each of these responses will draw out a distinction in Frege’s own philosophy of logic. The strongest arguments in favour of psychologism can be summarized as: the inseparability of logical and non-logical reasoning, the indemonstrability of primitive laws and the limits of thinking, the a posteriori nature of justified belief and, lastly, the mental subject matter of logic. Frege’s responses will call our attention to: the timeless nature of logical truths, the necessary conditions of objective truth, the meaning of logic as a priori knowledge, and finally the distinction between thought and idea.
To begin, we should understand that logic as a mental process of inference is therefore a human activity and so exists within a socio-historical context. Reason has a special and oppressive place within this context to which we should not be blind. Since Plato, Reason has been tied to both legitimizing power and making it exclusive in both explicit and implicit ways (Plumwood 11). Formal logic claims an absolute and timeless Truth void of both the oppression it exists in and the emotional attributes it thereby devalues (Plumwood 13). Consequently, it denies the experience of the oppressed as being unimportant to considerations of Truth. Logic also excludes the oppressed through its abstract notation, which requires background knowledge (i.e. university training or equivalent time expenditure) to which they would not have access. When logic is not in this power-laden abstract form, it is in the form of natural languages whose meanings and histories (of oppression) are inextricable. The very attempt to claim that logic does not suffer from the impurities of psychology, is a power-claim that must be understood in terms of its psychological-sociological context. Logic is therefore inseparable from psychology. The force of the above criticism comes from its appeal to a “common sense” association between logic and the elite environment in which it was developed. By questioning the intentions (conscious or otherwise) of those who do logic, the critic sidesteps logic as a subject matter and instead treats logic as an activity, which seems to only logically result in a psychologistic view of logic.
This first criticism is a point Frege indirectly addresses in the introduction to “The Foundations of Arithmetic”. If we were to treat logical-mathematical truths as subject to socio-historical contexts then “astronomers would hesitate to draw any conclusions about the distant past, for fear of being charged with anachronism,” (Frege Foundations VI). No matter how “Reason” may be abused over the course of history, the truths it ascertains are of a timeless nature. If they were not, then (as Heraclitus made clear) everything would be in flux and we could not know anything about the world (Frege Foundations VII). This response draws its strength from taking the very existence of knowledge as one of its premises, something no opponent can do while simultaneously maintaining a commitment to the objectivity of their own claim.
To this, critics from the oppressed groups can say, “At no point did we deny that there are timeless truths, we’ve only denied that one can effectively isolate them from contextual truths of oppression. Is the totalizing nature of your system not evidence of a bid to ignore the conditions of the oppressed?” Frege answers this question in his division between two kinds of proof. The first kind relies on the laws of logic alone, whereas the second also requires additional empirical facts (Frege Begrift. 103). Though the language of “purity” may misleadingly suggest some kind of normative superiority in the strictly logical kind of proof, in fact, these are simply two different kinds of proof. Claiming that logical proofs can exist alone no more devalues emotionality, than excluding ballet from biology devalues dance. Frege’s point is simply that such considerations are misplaced in his project. To criticize Frege’s logical language for failing to capture these everyday facts would be like blaming a microscope for failing to be a pair of eyes (Frege Begrif. 105). We can conclude from this that not only is it not necessary to appeal to socio-historic conditions when undertaking the study of logical truths, but, in fact, it is detrimental to that study. The first criticism is therefore refuted and the necessarily timeless nature of logical truths asserted.
Secondly, we may ask Frege what the origins of his logical rules are. He might respond that we have merely to examine our own thoughts to realize that everything we think (when we are thinking correctly) has a certain underlying structure. If a black board were nearby, he may write “x=x” and ask us if we disagree. No, but not because we can prove that “x=x” would always be the case in every possible world, but because we cannot imagine a world being otherwise. Indeed, if the final appeal in logic is always to limits on imagination and what we intuit to be true, if there are no further steps possible to prove the basic concepts of logic, then the limits of logic are the limits of thinking and that is very much a psychological topic. The force of this criticism lies in its appeal to the principle of sufficient reason ad infinitum. If something is being held as true, we as rational creatures want to know what reason we have for holding that. We then ask what reason we have for holding those reasons, etc. Stopping the justification seems to be necessitated by personal rather than objective rational limitations.
Frege makes it quite explicit in the introduction to the “Foundations” that his project is to ground mathematics in logical laws “which themselves neither need nor admit of proof,” (4). In a footnote he argues that the existence of any general truths at all necessitates the admission of such “primitive” laws, since, without them, we would never have any justification for believing anything--only procedures which induce belief (Foundations 4). If we must have these laws, let us then ask what kind of laws they are. We can understand these laws two ways. Firstly, “the laws” could mean that there is a certain reality external to the subjectivity of the thinker which limits what that thinker can think. Secondly, “the laws” might mean something inherent to the subjectivity of the thinker. To analogize: in the first case, the laws of thought are walls beyond which nothing sensical is, whereas, in the second case, there is merely a horizon which our eyes cannot see past. It is clear that the critics mean the second case.
If these basic laws are of the second kind, then the critics are right in concluding that logic is therefore a topic of psychology. Frege makes it very clear in his Thought paper that the basic laws are of the first kind. He says to mistake the laws of thought for the laws of thinking is to ignore the fact that what laws tend to is truth, whereas the laws of thinking would have to account for how one comes to error and superstition as well (290). Said differently, the logical laws deal with thought, which are objective logical entities, whereas the psychological laws deal with ideas which are subjective mental entities (Frege Thought 291-92). Thoughts are things for which the question of truth and falsity arise, whereas ideas are simply subjective mental occurrences. Even if it were the case that our minds only tended towards truth, to equate logical with psychological laws would be “to take a description of the origin of an idea for a definition,” which we should never do (Frege Foundations VI). After all, “an explanation of a mental process that terminates in an assertion can never take the place of a proof of what is asserted (Frege Thought 290). This becomes clear in the following analogy:
Suppose Bartholomew wants to get to his girlfriend, Truth’s, house. He walks west for a few blocks, then turns north a few more blocks. He passes three orange bushes and a one-eyed man playing a bronze tuba. He catches a bus going east at 60 miles an hour for fifteen minutes. Eventually, he arrives at a house. Do we, as the observers, know if it is the correct house? No.
No matter how excruciatingly detailed we are in our description of the steps Bartholomew takes to get to his girlfriend’s house, that alone could never indicate to us whether or not Bartholomew has arrived at the correct destination. If we are interested in knowing if he has arrived at the correct house, we must know something else, the correct path. Similarly, the laws of psychology describe how people take the steps people actually take to get to their particular mental destinations. These laws tell us nothing of whether or not the path was correct. It is the correctness of the path which logic is interested in, whether or not anyone ever takes it, or how they do is irrelevant to logic’s subject matter. We can therefore confidently reject the critic’s equivocation between the laws of thought and the laws of thinking. The second criticism is therefore refuted. As a result, we gain a more solid notion of the true subject matter of logic. It is “the path” inference, not as it happens to be taken by people (as a mental activity), but as it must be taken in order to reach the correct destination.
The third argument is perhaps the most historically grounded. Both John Locke and John Stuart Mill, at different times, have argued against the idea that a priori knowledge is possible. Locke argues that if any logical truths were really prior to observation, then children would readily admit them, but it is only after a certain abstract learning process in the world that these truths become known (273). What is important about this abstract learning process is that it must begin with concrete objects and observation and develop from there (Locke 273). Similarly, Mill argues that proof for believing in axioms consist in generalizing from observations (Kusch Sec. 2 Par 11). Perception and observation become indispensable for the proving of logical truths. Observation is unquestionably a topic for psychology, therefore logic, again, must look to psychology for its foundations. The strength of this claim rests on similar grounds to feminist critique. That is, the seemingly highly contrived and abstract nature of logic seems impossible to identify with anything other than a human activity, an impressive mental feat.
Given that truth is the aim of logic, logic must study whatever truth can be discerned from (Frege Mind 289). If truth and falsity were either physical objects or properties of physical objects then Locke and Mill would be correct. The question then arises, is truth (or falsity) a physical object or a property of physical objects? Is it possible to discern truth through the senses? Frege considers this possibility that truth comes to us from the senses in his Thought paper, quickly rejecting it (292). After all, if truth/falsity were properties of objects then it would make sense to say “the sun is true” in the same way that we might say “the sun is bright” or “the sun is a holy hippo” (Frege Thought 292). It does not make any logical sense to say “the sun is true” (though we might mean it poetically somehow). It does make sense, however, to say “the sun is bright” or “the sun is a foul-smelling bus passenger”.
Now we must ask: what does it mean for a sentence to make or have a sense? The answer to this question will make very clear the difference between the first sentence, “the sun is true,” and the others. According to Frege, “It is for the sense of a sentence that the question of truth arises…” (Frege Mind 292). This means that if a sentence has a sense, it must be possible to ask whether the sentence is true or not. Frege does not merely mean the sounds that make up the sentence, since sounds are no more true or false than the sun. It is what the sentence expresses that is true or not; what it expresses, Frege calls a “thought” (Frege Mind 292). At the risk of sounding slightly redundant, it is important to see that if we cannot ask whether a sentence is true or not than that sentence must not express a thought. Truth and falsity are therefore not properties of physical objects, but rather prompted by non-physical “thoughts”.
Let us return then to our original challenge and see what becomes of Locke and Mill’s claim. They say that physical objects must be observed in order to discern any truth (which is what logic attempts to do).We have already established that this is not true in any direct way because truth and falsity are neither physical objects themselves nor properties of objects (the sun cannot be true or false). Frege responds that truth and falsity are not properties of objects, but rather have to do with the thought a sentence expresses (which is a non-physical thing). Locke and Mill return that the thought needs to be about something and what it must be about are all physical objects. A logical statement expressing the thought “x=x” may refer to any physical object in particular, but, because of that fact, refers to no physical object in particular. What’s more, the truth of the above statement is made no more certain no matter how many particular objects are given as evidence. It follows solely from primitive logical laws which, according to Frege, make it an a priori truth (Foundations 4). Even if the sentence did pick out a particular object “that tree is that tree” it would be no less an a priori truth, since, according to Frege “these distinctions between a priori and a posteriori… concern… not the content of the judgement but the justification for making the judgement,” (Foundations 3). Locke’s insistence that children must learn these rules through sensory examples is not a problem for Frege since the origin of a belief is not the same as what proves that belief (in the same way that describing the path to a location, on its own, tells us nothing of whether the location is the desired one). In this way, the third criticism is safely refuted.
Lastly, there is the argument that logic’s abstract “objects” are mental entities and so naturally fit into the purview of science. “1. Logic is the theory of judgments, concepts, and inferences. 2. Judgments, concepts, and inferences are human mental entities. 3. All human mental entities fall within the domain of psychology. Ergo, logic is a part of psychology,” (Kusch Sec. 3 Par. 4). This argument is perhaps the most intuitive, since all three premises seem, at least at face value, uncontroversial. Indeed, the very need to argue against any of these premises would lend credence to Locke’s argument which relies on the need to perceive logical laws, rather than simply having always known them. The less obvious logical laws are, the more difficult it is to claim that they are somehow independent of the very particular (often academic) experience which creates them.
The last criticism, that logic is about judgements, concepts and inferences, these are all human mental entities, therefore logic is a subcategory of psychology has largely already been answered in past refutations. For clarity’s sake, however, we will examine this argument in its own right. It is clear that premise 1 “Logic is the theory of judgments, concepts, and inferences” is uncontroversial (Kusch Sec. 3 Par. 4). Logic does indeed cover all of these concepts and Frege himself discusses them quite plainly (Thought 294). Given this, it must either be premise 2 or 3 which are false, since the argument is itself seemingly valid. Judgements, concepts and inferences, it has already been shown cannot simply be mental entities in the same way that superstitions or emotions are since this would make the truths of math subjective (Frege Foundations VI). Logic does not study the judgements, concepts and inferences as mental occurrences (though they are sometimes), in the same way that the physicist does not study physical laws as experience, but as an independent subject matter. If we were incapable of distinguishing between the physical experience and the objective laws underlying and governing that experience, than physics to would be a branch of psychology. In fact, along this line of reasoning, everything would be reducible to psychology. This argument for psychologism is the broadest in scope, but for that reason goes too far in equivocating that which is both necessarily and sufficiently described as a mental entity (i.e. that which is essentially a mental entity) and that which need not be described in terms of a thinker (i.e. that which is only accidentally a mental entity). It is clear from the above that disciplines such as logic and physics which deal with the second kind of subject matter. The fourth and final criticism is therefore refuted.
To conclude briefly, I would like to make plain the errors common to multiple or all psychologistic arguments explored in this paper. All arguments to a greater or lesser extent confused the objective thinker-independent subject matter of logic with either the thinker-dependent experience of that subject matter (e.g. the learning of it) or else reducing it to thinker-dependent “ideas”. The strength of the criticisms lied mainly in their intuitive appeal to how one may feel about logic, but these arguments lacked the sophistication in distinction necessary to critique Frege’s true project. The recurrent appeal to the seemingly contrived nature of logic can be said to be the underlying motivation for all these criticisms and relies on a confusion between the form and content of logic.
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