What is the Connection between Our Reasoning Abilities and Our Psychology?
Our minds have an innate capacity for logic, which allows us to come to reasoned conclusions on the basis of information that is already given. The logical conclusions that we come to are not mere guesses nor are they feelings nor creative inventions. If one’s reasoning process is sound, then any conclusions would be logically entailed from that which was given at the start.
This includes logical operations that we can call “or”, “and”, “not”, “all”, “exists”, etc. A very common example begins which the two given statements: “All men are mortal” and “Socrates is a man”, from which we can derive the logical conclusion “Socrates is moral”. Ideally, the vast majority of philosophical and scientific conclusions should be logically entailed from the raw data and any fundamental assumptions that were known at the start of any research project. All mathematics can also be understood in terms of complex logical operations. This makes logic very powerful and very important to knowledge formation since we don’t often directly observe profound facts about the world directly. Instead, we rely on our reasoning capacity to develop a broader and deeper understanding of reality.
But how do we know that our logic is sound? How do we know that logic, as we know it, is true? How do we know that are reasoning capacity is entirely logical? This leads to the larger question of what is the ultimate basis of logic itself. Is logic an inherent feature of reality that we are capable of mentally understanding? Or is it just another arbitrary way in which we happen to think about things that is determined by how our brains are wired?
If our brains have an innate capacity for logic, then perhaps this means that our conception of logic is entirely based on our psychology, and is not necessarily a representation of anything in reality. This theory, known as psychologism, says that logic is essentially derived from our psychology. If logic ultimately comes from within our brains, and our brains are nothing more than neurons and chemical processes, then the product of this is entirely bound by the brain’s limited computational capacity. Psychologism says that the brain has limited thinking abilities and that, therefore, our logical conclusions are not necessarily mind-independently true. Rather, we have a conception of there being sound logic because our brains are wired to think that way as result of our evolutionary history, our genes, our education, and perhaps even our culture.
For example, we can consider “1 + 1 = 2”. Like all mathematical equations, this is ultimately based on logic. We know that “1 + 1 = 3” is wrong, but are we so sure? Is “1 + 1 = 2” a reflection of reality, or do we think that because of how our brains are wired? Could there be someone with a different perspective on the question of one plus one, perhaps because of their different genes or their different culture? If anyone in the world’s brain is wired to make them innately believe that “1 + 1 = 3” is sound reasoning, would that be equally valid to our contention that “1 + 1 = 2”? Any such person would seem illogical to us, but if we go with psychologism, then it would seem to imply that there is nothing inherently accurate about our supposed ability to tell the difference between sound logic and illogic.
Is the psychology of the mental processes of logic the ultimate basis for our secure belief in our logical reasoning capacity and any conclusions that we might come to through such reasoning? Twentieth Century philosopher Edmund Husserl argued that psychologism makes knowledge impossible because it is hopelessly relativistic and skeptical. As one commentator summarized:
Psychologism yields relativism, since logical validity is taken to depend on the contingent psychic make-up of the human being, since that a different make-up would produce different laws. And it yields skepticism since, by denying logic unconditional validity, it renders every truth-claim undecidable.[1]
We need a more solid foundation for logic than what psychologism would provide, otherwise we won’t be able to believe anything that we think could have universal validity. If we doubt our ability to reason soundly, if we are unsure whether we are actually understanding reality when we reason, then our very rational existence is questioned. There might be some innate irrationality in our nature and our ability to reason might not be perfect, but it is senseless to accept psychologism and the relativism and broad skepticism that it would bring. As Husserl said, “The correctness of the theory presupposes the irrationality of its premises, the correctness of its premises the irrationality of the theory”.
As an alternative, Husserl offered that logical laws have ideal validity. In a sense, we are understanding certain fundamental aspects of reality and of truth when we reason soundly, and this is made possible because of our ability to mentally grasp the universally valid ideas of pure logic. This ability is foundational for the construction of objective knowledge and for any sciences based on objectivity, such as physics, biology, and psychology. Whereas any objectivity-based science must have presuppositions about certain basic features of the universe and what constitutes evidence and how to gather data, logic must not be based on any presuppositions. Logic that makes sense needs no further basis for its justification, and it serves as an important basis for science itself.
[1]A Companion to Phenomenology and Existentialism p. 12
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