94. The third part of logic, which has for its object the several processes by which the human intellect arrives at knowledge by reasoning, treats: 1. of method in general and its laws; 2. of the different kinds of method and their laws; 3. of the processes peculiar to certain methods.
ART I. -- METHOD.
95. Method is the direction given to the cognitive faculties, according to their nature, to enable us easily and surely to arrive at knowledge. -- It does not suffice for the acquisition of knowledge that we know the laws governing the intellect, and what constitutes science itself; we must also know the way by which science is acquired, the particular path by which we may easily and surely attain to this or that science. This way or path which leads to science is method.
96. Both reason and experience prove the great importance of method. -- As we speedily and surely reach the end of a journey when we know the road, in like manner we easily and surely arrive at the knowledge of a science when we know the process which the mind should pursue. Ignorance of method necessarily causes much loss of time and often leads into error, a truth which experience likewise confirms. To good method is due the rapid progress of the natural sciences in late years; to a faulty method followed in philosophy in our own day, we owe the false systems which retard its progress.
97. Method should be neither artificial nor arbitrary, but should be founded on the nature of the mind and of the object which it studies. -- As method has for its aim the directing of the mind in the acquisition of knowledge, it must be based upon the very nature of the mind and of the object to be known. This is the fundamental law of all method. It gives rise to several others, which may be reduced to the two following: 1. We must in every method proceed from the better known to the less known; 2. We must proceed with order from one cognition to another.
ART II. -- ANALYSIS AND SYNTHESIS.
98. Two processes are common to all methods; 1. Analysis, which resolves a whole into its parts; and 2. Synthesis, which reconstructs the whole from the parts. -- The mind must perform two processes in order to arrive at knowledge. For either it seeks the nature of the whole by studying its parts, and thus proceeds from effect to cause, from the concrete to the abstract, from the multiple to the simple, as in abstraction and induction; or it studies the parts in the whole, proceeding from the cause to the effect, from the abstract to the concrete, from the simple to the multiple, as in deduction. The first process is analysis; the second, synthesis.
But a method can be neither purely analytical, as the Experimental and Sensualistic school pretends, nor purely synthetical, as the Idealistic school holds. It cannot be purely analytical, since, to constitute science, it does not suffice that we know by analysis the whole through its parts, or the cause through its effects; we must, moreover, know by synthesis how the whole contains the parts, how the cause produces the effect.{1} On the other hand, method cannot be purely synthetical, since it belongs to the nature of the mind to know the whole in its parts and the cause in its effects. We must, therefore, conclude that all method, to be good, ought to be analytico-synthetical.
99. The rules for analysis are: 1. It should be complete; 2. It should be as extensive as possible. -- The rules for synthesis are: 1. It should omit nothing in the consideration of the whole; 2. It should add nothing. -- Analysis makes known the whole in the parts, the simple in the multiple, the cause in the effect, only in so far as it investigates each of the parts and each of the effects. If it neglect to consider any one, it is liable to overlook one of the essential elements of the whole. In the second place, it must divide and subdivide the whole into a reasonable number of parts, since the less complex a thing is, the better the mind knows it. Synthesis should neither omit nor add anything: for in the former case it would give only a partial or incomplete view of the object; in the latter, it would introduce foreign elements, and thus alter our notion of that object.
{1} Our knowledge in particular cases is, however, often limited to the mere fact that the cause produces the effect.