Refutation of Their Claim That Every Demonstration Must Contain a Universal Premise

Moreover, they contend that theoretical, certain knowledge can be attained only through demonstration, which for them is a syllogism of universal scope, and that such a demonstration must include an affirmative universal proposition.

Accordingly, they declare that no conclusion can follow from two negative premises or from two particular premises in any kind of syllogism—whether we look at its form (categorical, hypothetical conjunctive, or hypothetical disjunctive) or its matter (demonstrative, rhetorical, dialectical, or even poetical).

We reply: if every proof they call a demonstration must contain a universal premise, then one must already know that premise and know that it is universal. The moment one admits that it might be particular rather than universal, certainty collapses. As for the so-called “indefinite” (muhmala) proposition—an unqualified statement whose wording could be read as either universal or particular—it effectively functions as a particular.

Since the certainty they derive from the syllogism they reserve for the name “demonstration” depends on knowledge of an affirmative universal premise, we say: if knowledge of that premise is self-evident, then, a fortiori, knowledge of each of its individual instances could also be self-evident. If, on the other hand, the premise is theoretical, it must rest on some self-evident knowledge; this leads either to a vicious circularity occurring at the same level or to an infinite regress in matters that do in fact have a beginning. When the knowledge of the son of Adam depends on another of his cognitions, and that on yet another, his knowledge must have a starting point, because he himself has a starting point. This is not like a mere regress in past events; rather, it is a regress in causal agents, and both alternatives are impossible.

The same reasoning applies to every other universal proposition they regard as a first principle of demonstration and label “necessary to accept,” whether the data in question are outward sensory perceptions or inner sensations that a person feels within himself.