RELATIVITY OP KNOWLEDGE, a philosophical doctrine that is almost a commonplace in some philosophical schools, and is as strenuously denied by others. It is connected primarily with the contrast between the absolute and the relative, or the noumenon and phe nomenon, and is one phase of the great discussions as to the relation of knowl edge to reality. In its modern form the doctrine has obtained currency chiefly through the speculations of Kant, Ham ilton, and Herbert Spencer. Knowledge evidently implies a knower and a rela tion between the knower and the object known. Hence it is argued that the ob ject is conditioned by the relation into which it is brought; merely by becoming an object the thing as it is in itself un dergoes a change or accommodation. Our knowledge therefore can never yield us the reality of things—the noumenon or thing-in-itself—but only the phenome non, the thing as it appears to us. Or, as it is otherwise expressed, in being known the object must conform to the nature of the knowing faculty; the men tal constitution or organization of the knower; we cannot, therefore, conclude, says Hamilton, that the properties of ex istence are known "in their native purity and without addition or modification from our organs of sense, or our ca pacities of intelligence." Hamilton's general conclusion is: "Of things abso lutely or in themselves, be they external or be they internal, we know nothing, or know them only as incognizable; and we become aware of their incomprehensible existence only as this is indirectly or ac cidentally revealed to us, through certain qualities related to our faculties of knowledge. All we know is therefore phenomenal, phenomenal of the un known." This is adopted by Spencer, and made the basis of his theory of knowledge, or rather of what Ferrier would have called his agnoiology, his doc trine of our necessary ignorance: "The reality existing behind all appearances is, and must ever be, unknown." In
Kant a similar doctrine is associated with the asserted subjectivity of the forms of space and time; but it is also based on the broader consideration that perception can give us "only the rela tion of an object to the subject, not the inward essence which belongs to the ob ject in itself." The empirical schools, which resolve our knowledge into im pressions of sense manipulated accord ing to the laws of association, likewise accept in its widest sense, as J. S. Mill points out, the doctrine of "the entire inaccessibility to our faculties of any other knowledge of things than that of the impressions which they produce in our mental consciousness." But, inas much as they in many cases profess a skeptical idealism which denies, or leaves doubtful, the existence of any reality be yond the states of consciousness, their views are less usually associated with the term.
The doctrine is frequently based on the large extent to which sensation en ters into all our knowledge. In the structure of their sense organs different living creatures differ appreciably, and there will be a corresponding difference in the image of the world which they make to themselves. The knowledge of every being, it is argued, is thus inevit ably conditioned by its organization, and there is no possibility of arriving at an objective criterion. Man, in the Protag orean formula, is the measure of all things; but he measure them only as they seem to him. Such a formula may be interpreted either in a sensational istic and individualistic fashion, as seems to have been done by Protagoras, or in a rationalistic and humanistic fashion, as is seen in Kant. The case for the relativity of knowledge will be found strongly put in Sir W. Hamilton's "Dis cussions and Lectures on Metaphysics," in Dean Mansel's "Bampton Lectures," and in Herbert Spencer's "First Prin ciples."