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Aristotle’s syllogism and scientific knowledge


By David Reynolds

To say that Aristotle was a prominent philosopher would be an understatement. He studied under Plato’s tutelage, he became the tutor of Alexander the Great, and he sired syllogistic logic. Aristotle was one of the greats. Perhaps the most enduring element of his philosophical meditations has been his syllogistic logic. To facilitate a better understanding of this, it is helpful to contextualize and explain what constitutes the syllogism and scientific knowledge in Aristotle’s epistemology.

Aristotle had loved truth more than the ideas of Plato, and he deviated from those teachings. A significant difference arose as Aristotle disagreed with Plato’s theory of the Forms. While Aristotle sought to discover universals, he did not hold that universals existed separately from their particular cases; he claimed that universals consisted of the collection of particulars and there was no appeal to some abstract Form. In the Posterior Analytics, Aristotle considers the nature of the relationship between universals and particulars. It is here that he discusses the syllogism, demonstration, and scientific knowledge, and here he relates the differences between his own ideas and those of his tutor, Plato.

Aristotle asserts that our knowledge of events comes from demonstration (71b.18). He makes this claim after addressing the dilemma of Plato’s Meno – that is, if knowledge is recollection, “either a man will learn nothing or what he already knows” (71a.29). The problem with this recollection theory of knowledge, as Aristotle points out, is that it renders the notion of learning meaningless: “the strange thing would be… if he were to know [something] in that precise manner in which he was learning it” (71b.8-10). Furthermore, Aristotle will affirm that scientific knowledge is a matter of understanding the cause of an event (71b.9-12), an understanding which need not be derived from some recollective sense of knowledge.

The essence of Aristotle’s view of attaining scientific knowledge is summarized in the following passage:

What I now assert is that all events we do know by demonstration. By demonstration I mean a syllogism productive of scientific knowledge, a syllogism, that is, the grasp of which is eo ipso such knowledge. Assuming then that my thesis as to the nature of scientific knowing is correct, the premises of demonstrated knowledge must be true, primary, immediate, better known than and prior to the conclusion, which is further related to them as effect to a cause. Unless these conditions are satisfied, the basic truths will not be “appropriate” to the conclusion. (71b.18-23)

Unfortunately, this passage may be difficult for some readers to fully and accurately interpret due to the large amount of loaded terminology. Thus, an explanation of the complex terms and their relevance follows.

Aristotle argues here that we uncover scientific knowledge through his logical syllogism (71b.18-20). His syllogism is the “recognition through a middle term of a minor term as subject to a major” (71a.24-25). Accordingly, the following is a logical syllogism:

All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal.

The conclusion follows from the truth of the premises where “men/man” is the middle term, “Socrates” is the minor, and “mortal” is the major. The syllogism functions such that the given premises lead us to, presumably, new information in the conclusion by means of the shared middle term in the premises.

However, Aristotle asserts that there are further criteria to be fulfilled before the syllogism will yield scientific knowledge. Before the syllogism can produce scientific knowledge, Aristotle requires that the premises “must be true, primary, immediate, better known than and prior to the conclusion” (71b.21-22). With these qualifications, Aristotle’s empiricist tendencies become evident. That the premises must be true places them as affirmations regarding existence, “for that which is non-existent cannot be known” (71b25-26). The premises must be primary and immediate in so far as they require no further appeal to account for their truth (71b.27-29). This also avoids the chance of infinite regress in founding the premises. When Aristotle requires that the premises be better known than the conclusion, he means there must be a particular in the given premises – that is, particulars are examples known to our senses and this restricts our truth claims to phenomena within the sensible realm (72a.1-5). Furthermore, Aristotle places the premises as prior to the conclusion because he claims that the premises cause the conclusion, and that scientific knowledge is only made clear upon discovery of the cause (71b.29-32). These conditions are meant to empower the syllogism to yield scientific knowledge without committing a fallacy.

As Aristotle asserts that scientific knowledge can only be demonstrated by the account of such a rigorous syllogism (72a.25-26), he effectively restricts scientific knowledge to that which can be observed in experience; he limits our knowledge to the a posteriori. With this theory of knowledge, Aristotle continues to argue against Plato’s a priori recollection theory of knowledge later in the Posterior Analytics. He claims that the a priori recollection of knowledge requires us to have an innate possession of apprehensions more accurate than those that demonstration could provide (99b.26-28). In the light of Aristotle’s argument, this seems counterintuitive.

Aristotle’s account of empirical, scientific knowledge is appealing and appears to be quite legitimate. However, while I agree with the notion that a posteriori sense perception is crucial in scientific accounts of the world and its causes, I do not feel that the syllogism’s premises need to have Aristotle’s degree of immediacy. Arguably, neither scientist nor philosopher has ever accomplished a solid foundation for scientific knowledge. As such, it is doubtful that we could know any premise as an immediate truth. Further, science builds upon its discoveries with a significant degree of accuracy. Surely, if science were to employ the syllogism as Aristotle prescribed it, then they would need to dismiss the immediacy criterion as it would hinder scientific progress. Nevertheless, that may be nitpicking over trivial matters.

The essence of Aristotle’s syllogism and account for scientific knowledge has endured much criticism and the test of time. The ideas he fostered have flourished and evolved throughout the history of philosophy. Aristotle affected philosophy, scientific knowledge, even the way we think about the world around us in a profound manner with his ideas about the nature of knowledge and the role of logic.

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