of the form of the proof resembles a person’s reckoning of his holdings in slaves and real estate. The innate disposition grasps a sound syllogism without instruction. People naturally employ the three forms—inclusion, implication, and division—just as they employ arithmetic and the like. The logicians may concede this.
In short, we do not deny that a syllogism yields knowledge when its premises are known with certainty. But we say:
The knowledge obtained through it does not require the logical syllogism; rather, it can be obtained without it. Thus, no knowledge depends upon this syllogism. Moreover, the certain premises they enumerate yield no knowledge of existing things. They therefore achieve no purpose through which souls are purified, nor even knowledge of realities in the external world as they actually are, except of the same kind as that obtained through analogical reasoning. No knowledge can ever be obtained through the inclusive logical syllogism, which they call demonstrative, without that same knowledge also being obtainable through analogical reasoning, which they regard as weak. For that syllogism must contain a universal proposition.
Yet certainty that a universal proposition is indeed universal is impossible without certainty that its individual instances are alike in what they share—and this is established through analogical reasoning.
We shall explain this in several ways.
First:
They have restricted premises known with certainty to the categories familiar to them.