Chapter 68

One must know that there are four dialectical or logical methods. That is by division which divides the genus into species by means of the intermediate specific differences. That is by the definition which defines the subject by the genus and the specific differences divided out by the method of division. That is by analysis which resolves the more composite thing into its simpler elements. Thus, the body is resolved into the humors; the humors, into the fruits; the fruits into four elements; the elements, into matter and form. That is by demonstration which proves the matter at hand by means of something intermediary. For instance, I have to prove that the soul is immortal, so I take an intermediary, namely, the being ever in motion, and I reason as follows: The soul is ever in motion. But, that which is ever in motion is immortal. Therefore, the soul is immortal.

It must further be known that syllogisms belong to the method by demonstration. And one must know that the analytical method is of three kinds. Thus, it may be natural, as in the example cited above. We also have logical analysis when we resolve the proposed syllogism into its proper form; and we have mathematical when we take the thing asked for granted and thence arrive at something which is acknowledged to be true and from which the proposition is proved. For example, let the question be: Is the soul immortal? I take for granted that which has been asked and I say: Since the soul is immortal, there is a reward for its bad and good actions. Now, if there is such a reward, then there is that which is passed judgment upon and that which passes judgment. But, if there is that which is judged and that which judges, then there is a provider and a providence. And so we have arrived at providence, which is acknowledged by everyone. From this point on I put things together and say: Since there is a providence and a dispenser of justice, there are also rewards. And since there are rewards, there is that which is judged. But, if there is that which is judged, then the soul is immortal.

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