If the criterion is the external form, then restricting the shape of a proof to five or six figures is no sounder than restricting it to two premises. A proof can be cast in many different guises that involve neither a connected nor a disjunctive conditional, and that are not framed as the categorical syllogism they describe. If, on the other hand, the criterion is meaning, that is an even clearer refutation of what they have asserted; for the meaning is simply that the evidence must entail the conclusion, whether that entails one premise, two, or more, and whether it appears in the order and arrangement they lay down or in some other pattern.
The correct judgment in this matter is that, even when what they say happens to be right, it only lengthens the road, pushes the objective farther away, and turns the very aim on its head. They claim to have fashioned a formal tool that will keep the mind from stumbling in its reasoning; yet when they oblige the inquirer to adhere to it in all his conceptions and assents, it actually brings him nearer to error and further from his goal—as experience testifies. You will not find anyone who has bound himself to their framework and terminology without being more prone to mistakes and less apt to hit the mark than someone who forgoes their conventions and reaches his objective through the innate disposition with which Allah has endowed His servants. Indeed, no one who has truly mastered any science has ever been enslaved to their procedure.
Hence it is said: the proliferation of these figures and the conditions for deriving conclusions from them is a lengthy business, low in benefit and high in toil. It is like the lean flesh of a camel perched atop a rugged mountain—neither easy to climb and obtain, nor worth the effort once obtained. Whenever the material is sound it can be cast in the first, natural figure; the remaining figures are unnecessary. Their sole utility lies in being reduced to that first figure—either by refuting the contradiction that the reductio ad absurdum entails, or by simple conversion or conversion of the contradictory. For once one of two contradictories is affirmed, the other must be negated, provided the opposition is complete. Thus they infer from the truth of a proposition the falsity of its contradictory, and the truth of its converse and the converse of its contradictory. In truth, the mind’s picturing of a proof is like a man keeping accounts of his servants and real estate.
By sheer natural disposition the mind grasps a valid syllogism without instruction, and people by nature speak in the three modes—implication, entailment, and division—just as they talk of arithmetic and the like, whereas the logicians