BOOK III (B)
Chapter 1
We must, with a view to the science which we are seeking, first recount the subjects that should be first discussed. These include both the other opinions that some have held on certain points, and any points besides these that happen to have been overlooked. For those who wish to get clear of difficulties it is advantageous to state the difficulties well; for the subsequent free play of thought implies the solution of the previous difficulties, and it is not possible to untie a knot which one does not know. But the difficulty of our thinking points to a 'knot' in the object; for in so far as our thought is in difficulties, it is in like case with those who are bound; for in either case it is impossible to go forward. Therefore one should have surveyed all the difficulties beforehand, both for the reasons we have stated and because people who inquire without first stating the difficulties are like those who do not know where they have to go; besides, a man does not otherwise know even whether he has found what he is looking for or not; for the end is not clear to such a man, while to him who has first discussed the difficulties it is clear. Further, he who has heard all the contending arguments, as if they were the parties to a case, must be in a better position for judging.
The first problem concerns the subject[1] which we discussed in our prefatory remarks. It is this—whether the investigation of the causes belongs to one or to more sciences,[2] and, if to one, whether this should survey only the first principles of substance, or also the principles on which all men base their proofs, e. g. whether it is possible at the same time to assert and deny one and the same thing or not, and all other such questions.[3] And if the science in question deals with sub-
