The principles of science : a treatise on logic and scientific method / by W. Stanley Jevons.

  • Jevons, William Stanley, 1835-1882.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: The principles of science : a treatise on logic and scientific method / by W. Stanley Jevons. Source: Wellcome Collection.

    31/488 (page 11)
    TJie Process of Inference. The fundamental action of our reasoning faculties consists in inferring or carrying to a new instance of a phenomenon whatever we have previously known of its like, analogue, equivalent or equal. Sameness or identity presents itself in all degrees, and is known under various names; but the great rule of inference embraces all degrees, and affirms that so far as there exists sameness, identity or likeness, what is true of one thing will be true of the other. The great difficulty of reasoning doubtless consists in ascertaining that there does exist a sufficient degree of likeness or sameness to warrant an intended inference ; and it will be our main task to investigate the conditions under which the inference is valid. In this place I wish to point out that there is something common to all acts of inference however different their apparent forms. The one same rule lends itself to the most diverse applications. The simplest possible case of inference, perhaps, occurs in the use of a pattern, example, or, as it is commonly called, a sample. To prove the exact similarity of two portions of commodity, we need not bring one portion beside the other. It is sufficient that we cut a sample which exactly represents the texture, appearance, and general nature of one portion, and according as this sample agrees or not with the other, so will the two portions of commodity agree or differ. Whatever is true as regards the colour, texture, density, material of the sample will be true of the goods themselves. In such cases likeness of quality is the condition of inference. Exactly the same mode of reasoning holds true of magnitude and figure. To compare the size of two objects, we need not lay them alongside each other. A