Commentary on Husserl's Logical Investigations, Prolegomena Ch 4 

By Jeremy Hausotter

Chapter 4: Empiricistic Consequences of Psychologism

§21 Two empiricistic consequences of the psychologist standpoint, and their refutation

To understand this chapter, it is perhaps best to begin with the very last words of the chapter for this passage is the hermeneutical key to the whole chapter and Husserl’s wider project. Husserl writes: 

Such absurdities are unavoidable if the fundamental distinction between ideal and real objects, and the corresponding distinction between ideal and real laws, is disregarded or misunderstood. We shall see repeatedly how this distinction settles the disputes which divide psychologistic logic from pure logic. (p. 110). 

The absurd consequences that arise from the psychologistic interpretation of logic is due, according to Husserl, to a fundamental confusion of real and ideal objects. Real objects, if we recall, are the topic of traditional Aristotelian logic, of substances, accidents, space, and time. Ideal objects, on the other hand, cannot be encapsulated in the Aristotelian paradigm of the ten categories of being nor within space and time. The confusion of these two types of objects is the fundamental problem of psychologistic logic and it manifests itself in many ways. 

In the first section of the chapter Husserl identifies two immediate problems. He begins by considering the epistemological status of psychological laws. Psychology lacks “genuine and therefore exact laws” (p. 98). Psychological laws are hence vague. By “vague” Husserl is using the term as a foil to “exact”. It is not meant to demean psychology but to emphasize an important epistemological fact on the status of psychological laws. Husserl clarifies this meaning of “vague” in footnote 1 (ibid). By vagueness then, psychological laws are generalizations of experience and are “approximate regularities of coexistence and succession” lacking “infallible, unambiguous definiteness” (ibid). This leads us to two immediate conclusions about logic. 

First, “only vague rules could be based on vague theoretical foundations” (ibid). Since psychological laws are vague, and so not exact, then this must also be true of logic under the psychologistic framework. The laws of logic are hence “infected with empirical vagueness” (p. 99). But such a consequence betrays a fundamental truth about logical laws being of “absolute exactness” (ibid). Establishing the laws of logic within psychology violates this truth because logic would now depend on an empiricism and circumstances. Husserl will later develop what is meant by “exact”. 

Second, the psychologist cannot escape this objection by claiming that logic is the result of an exact natural law. Here is what Husserl wrote and the following paragraph will be focused on it. 

No natural laws can be known a priori, nor established by sheer insight. The only way in which a natural law can be established and justified, is by induction from the singular facts of experience. Induction does not establish the holding of the law, only the greater or lesser probability of its holding; the probability, and not the law, is justified by insight. Logical laws must, accordingly, without exception, rank as mere probabilities. Nothing, however, seems plainer than that the laws of ‘pure logic’ all have a priori validity. They are established and justified, not by induction, but by apodeictic inner evidence. Insight justifies no mere probabilities of their holding, but their holding or truth itself. (p. 99). 

Husserl replies to this objection that natural laws are not a priori nor do we have access to them through insight. Natural laws are “established and justified… by induction from singular facts of experience.” (ibid). Logic is distinguished from natural laws epistemologically by ways we have access to them. Logical laws require insight whereas natural laws require induction. One consequence of this is that natural laws do not establish an a priori law, a law that is necessarily true absolutely, but one that either has higher or lower degrees of probability of being true. Logical laws are not probabilities but possess “a priori validity”. Logical laws “are established and justified, not by induction, but by apodeictic inner evidence.” (ibid).  The laws of logic have an inner content and evidence that convicts us of their absolute exactness and necessity. Our access to this inner evidence is through insight.


To summarize then, Husserl is arguing that we have epistemic access to logical laws through insight. This insight presents us with an “apodeictic inner evidence” that convicts us of logic’s a priori exactness. If we recall a statement Husserl made the previous page, this inner evidence informs us that logic possesses an “infallible, unambiguous definiteness”, meaning that we can be absolutely certain that the content of our insight is necessarily true. One last observation we can make is that it is assumed that the probabilities themselves are themselves justified to be true and themselves not also probabilities, otherwise we would have to be skeptical of not only the laws but also the probabilities behind the laws, (as Husserl writes “the probability, and not the law, is justified by insight.” (ibid) ). But why should these probabilities themselves be justified by insight and not the laws of logic? 

The laws of mathematics and logic do not possess possibility. They are not surmises based upon observed experiences. Some may argue that these laws are approximations to genuine laws beyond our reach like the natural laws, but as Husserl said, the natural laws such as the law of gravitation possess a vagueness. There is a family of formulations that can all be used to describe this law due to the inherent uncertainty of natural laws. For logical laws, on the other hand “we have insight into, not merely the probability, but the truth of the logical laws.” (p. 100). The inner evidence of logical laws convicts us of their truth. 

The consequences of the psychologistic view of logic are hence absurd since this view cannot describe features of logical laws such as insight, inner evidence, a priori exactness, etc. Hence Husserl concludes “Against the truth that is itself grasped with insight, the strongest psychologistic argument cannot avail: probability cannot wrestle with truth, nor surmise with insight.” (ibid). 

§22 The laws of thought as supposed laws of nature which operate in isolation as causes of rational thought


Husserl now takes up the task of investigating an “attitude” of the psychologists. It is held by them that:


The laws of thought count as natural laws characterizing the peculiarity of our mind qua thinking, and the essence of the conformity, as definitory of correct thinking, lies in the pure operation of these laws, their non-disturbance by alien influences (such as cushion, inclination, tradition). (p. 101). 

This view leads us to the following consequence: laws of thought then “could only be stated in the forms of probabilities. On this basis, no assertion could be certainly judged correct.” (ibid). Logic as natural laws of thinking requires these laws to be vague, approximations or probabilities but never with apodictic certainty. Hence, the very content of logic as inquiry into truth content and as an ethics of thinking (cf. p. 94) is itself no longer possible. No assertion on a truth content can be said to be correct or incorrect if such assertion was only probable, only likely true or likely false, but never definitively true or false. It follows then that there are no true assertions (which itself is an irrational belief for it is self-referentially inconsistent. One would have to say that all propositions cannot be known to be true with absolute certainty but this proposition itself must be taken in precisely this manner or it is otherwise also merely a probable statement, and if probable, then such a possibility of absolute certainty can be the case and so what purpose remains for the original proposition?).

One immediate consequence of the psychologistic view besides a fundamental betrayal of the phenomenon of logic itself, is that every assertion of knowledge itself is probable, and hence contains some error. Every successive assertion premised upon the first accumulates error, meaning that as the process tends ad infinitum, the error becomes so great that we can say there is no such thing as knowledge. We would have to be skeptical of any claim to knowledge. If premise 1 is 50% probably true, and likewise for premises 2, 3, etc, then the probability of premise 1 and 2 being true is 25%, premise 1, 2 and 3, 12.5%, and the first 50 propositions two to the power of negative fifty.  The cumulative error implies that there is no knowledge. The solution to this problem Husserl proposes is the direct insight into the apodeictic inner evidence of logical laws by which we can be certain of their truth (“Sceptical awkwardnesses would of course vanish if one looked on the laws of thought as matters of direct insight” p. 102).

This raises questions as to motives for why one would adopt the psychologistic thesis in the first place. Husserl observed two general confusions. The first was that logical laws were confused with judgments: “the laws, as ‘contents of judgment’ have been confused with the judgments themselves…” (ibid). In confusing contents with judgments themselves, these thinkers thereby place the contents of judgment within psychology since judgment itself is a mental activity. This confusion is really a confusion of what is real versus what is ideal. Judgments themselves as mental activities are something real but the content of judgments need not be as in the case of mathematics and logic. 

The second confusion is that laws as a term in causation is confused with laws as the rule of causation (ibid), treating the rules of causation as causes themselves. Logical laws were hence considered to be “causal laws of thinking” (ibid).

Against these confusions that motivated the psychologism of logic, Husserl argued by counterexample. He gives two examples. If we imagine an ideal person whose thinking is perfectly consistent with logical laws, then the causal laws according to which thought must proceed still cannot be identified with logical laws. Husserl then gives the example of a computer (keep in mind he is writing this decades before computers were invented). Computers are regulated by logical laws in their programming but their functioning and processing is due to mechanical laws of circuitry, electricity, etc. Logic regulates correct operations of the computer, but logic does not explain how the physical components work together to display on a screen nor how the keyboard receives its electrical inputs in every keystroke and how they are interpreted as the different characters on the screen. It would be a grievous error to confuse the mechanical laws governing the functioning of a computer with logical laws which only serve to regulate its processes. 

The errors here arise due to the confusion of ideal and real laws. “The psychologistic logicians ignore the fundamental, essential, never-to-be-bridged gulf between ideal and real laws, between normative and causal regulation, between logical and real necessity, between logical and real grounds. No conceivable gradation could mediate between the ideal and the real.” (p. 104). There is no gradual change from ideal to real as there is from black to white with the many shades of grey, but a sharp gulf and contrast, a strict demarcation between ideal and real. These errors betray a poverty status in logic studies. 

§23 A third consequence of psychologism, and its refutation

Husserl next outlines a third consequence of psychologism. If the laws of logic have their epistemological source in psychology, then logic itself must be “psychological in content, both by being laws for mental states, and also by presupposing or implying the existence of such states.” (p. 104). The psychologistic view of logic requires logic itself to be a mental activity for otherwise it would not be psychological. This view also requires logic to be concerned about the existence of such states, whether presupposing its existence or implying it. Husserl replied that “no logical law, properly understood is a law for the facticities of mental life…” (ibid). The content of logic is truth and falsity, not mental states. The laws of logic, once properly understood, “presuppose nothing mental, no facts of psychic life, whether in their establishment or their content.” (p. 105). The psychologistic view of logic requires us to deduce facts from pure law. 

We must now inquire what is meant by this distinction between facts and pure law. Husserl distinguishes between three types of laws. Empirical laws have a factual content. They are not true laws but speak of general patterns for particular circumstances, more specifically, “they merely say… that certain coexistences or successions obtain generally in certain circumstances, or may be expected, with varying probability, in varying circumstances.” (p. 106). They are generalizations of observations of fact. These laws are not only concerned with facts but also “imply their existence” (ibid). 

Exact laws are distinguished from empirical laws in that they are formulated as pure laws which “exclude all factual content” (ibid). They are distinguished from exact laws epistemologically for their proofs are due to the scientific method and hence are not established in the same manner as pure laws. Husserl gives the example of the law of gravitation. This law is never formally proved. Instead, we know that this law has a high probability such that we know that reality behaves like Newton’s formula or something similar to it. The exact laws of the natural sciences are genuine laws, but their epistemological status is that of “idealizing fictions with a fundamentum in re” (ibid). The scientist takes observations and patterns to determine with “apodeictic probabilities” knowledge of the real to find laws which govern and build up the different theoretical disciplines of natural science. These laws hence are ideal possibilities of real content. These laws are vague in that there are other formulations that can be included within their limits. 

Pure laws in the realm of factual knowledge remains an ideal towards which the natural sciences strive but only reach towards with higher degrees of probability. When we consider pure laws in the realm of “purely conceptual” knowledge, on the other hand, then this is the sphere where pure logic and pure math resides. These laws are free from existential content, and hence why this lack of freedom makes the laws of natural sciences probabilistic. Pure laws have entire validity in what they say and are given with absolute exactness. Pure laws exclude all other possibilities. When one has an insight into a logical law, he knows that this revealed content must be true with certainty and necessity. 

Psychologism requires that “logical laws do not merely entail existential assertions of mental facts, but are also laws for such facts.” (p. 107). Logic in the psychologist paradigm requires that logic is asserting existential content of mental activities and that logic regulates these. The laws for these facts are themselves epistemologically established through empirical observation and induction, meaning that these laws contain inseparable existential content. Pure laws of logic and mathematics do not refer to things but to pure objects in general. Husserl used the example of 2< 3. This is stating that the number 2 itself is less than 3. It is not an assertion about two things and three things, but about the pure numbers 2 and 3 itself.

§24 Continuation


Some now may object to Husserl’s argument that “not every law for facts has an emprico-inductive origin.” (p. 108). These objectors may argue that a distinction needs to be made between empirical and inductive laws. Logic is inductive and not empirical, for the concepts of logic are abstracted from psychological experience and combined with conceptual relations. The individual case is true because the law rests on generalized abstractions. 

Husserl replies that this objection “will not do.” Logic certainly presupposes the experience of persons since logic is an act of the mind. Husserl points out however that we must distinguish between the psychological preconditions or “presuppositions” for possessing knowledge of logic with the “presuppositions” for logic itself, which are the grounds and premises of that law. (ibid). We must certainly use our minds in contemplating the objects logic, but this cannot be confused with the objects of logic itself. From this it follows that the psychologist likewise confuses psychological dependence with “logical demonstration and justification”. In doing so, the psychologist confuses an “insight into the objective relation of ground and consequence” with psychological relations of succession and coexistence (p. 109). Logic at the very least requires two psychological steps of viewing a singular and then an insight into logical law, but logically there is only a single step. “The content of insight is not inferred from singulars.” (ibid). 

We must be clear that “All knowledge ‘begins with experience’, but it does not therefore ‘arise’ from experience” (p. 109). The laws of logic must be distinguished from facts. Facts are opposed to logic in that facts are determined by time, logic is not: “No truth is a fact, i.e. something determined as to time.” (ibid). Truth can refer to changing states within time, but truth itself is “raised above time”. (p. 110). If the laws of logic were real laws, then they would be determined by time and be “rules for the coexistence and succession of facts.” (ibid). This raises an absurdity however. Husserl notes that if this is what we mean by logic, as the succession of facts, then “the law would arise and perish in conformity with the law…” (ibid). If logic was a law of the real, then this law itself is temporally contingent and is its own principle of annihilation and creation. These absurdities can be avoided only if, as Husserl reminds us, we keep in mind the distinction between ideal and real objects, and ideal and real laws. 

We must note now that there can be a point of contention in Husserl’s statement that all logic begins with experience. The concept of experience is something Husserl is going to radically develop later in the Logical Investigations (cf. p. 249, 539-541). For now we will note that this development is a basic distinction made between “empirical” experience and experiences of ideal objects. The first is experiences of real facts, the second is an encounter with an object outside of what is real. 

There is a question now that I have. Husserl showed that logic would necessarily have to be an object outside of real existence, for if logic was real, then the absurdities would arise which he criticized. My question is metaphysical: is existence itself, according to Husserl, divided into two modalities of ideal and real, and or is existence strictly identified with what is real. The second would seem to be rather absurd to hold.  

Returning now to the text, Husserl observed that all logics of pure logic have the same character (p. 109). Husserl argued then that if some of the laws of logic cannot be regarded as psychological laws, then none of them can. His support for this conclusion is the fact that some logical laws “concern truths… have truths as their regular ‘objects’ ” (ibid). Truth itself is not something psychological, hence laws concerning truth must themselves likewise be non-psychological and so pure logic cannot be interpreted according to the psychologist paradigm. 


Another important point is that now Husserl distinguishes between fact and truth according to time. Truth is atemporal, independent of time, whereas facts are “determined by time” (ibid). Facts are bound by time whereas “the truth itself is… raised above time” (p. 110). This is in part why the laws of logic are not real laws, for if they were real laws then they would be determined by time. This would give rise to the problem that logical laws would come in and out of existence in temporal succession which is absurd; “The law would arise and perish in conformity with the law…” (ibid). As we stated in the beginning, we must keep in mind the sharp distinction between real and ideal objects, and between real and ideal laws. It is this confusion that underlies psychologism and gives rise to the several absurdities laid out in this chapter. 

Looking Down Yosemite Valley, California by Albert Bierstadt

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