Julian Lowell Coolidge

The Elements of Non-Euclidean Geometry Julian Lowell Coolidge

The heroic age of non-euclidean geometry is passed. It is long since the dayswhen Lobatchewsky timidly referred to his system as an 'imaginary geometry', and the new subject appeared as a dangerous lapse from the orthodox doctrineof Euclid. The attempt to prove the parallel axiom by means of the other usualassumptions is now seldom undertaken, and those who do undertake it, areconsidered in the class with circle-squarers and searchers for perpetual motion-sad by-products of the creative activity of modern science. In this, as in all other changes, there is subject both for rejoicing and regret. It is a satisfaction to a writer on non-euclidean geometry that he may proceedat once to his subject, without feeling any need to justify himself, or, at least, any more need than any other who adds to our supply of books. On the otherhand, he will miss the stimulus that comes to one who feels that he is bringingout something entirely new and strange. The subject of non-euclidean geometryis, to the mathematician, quite as well established as any other branch ofmathematical science; and, in fact, it may lay claim to a decidedly more solidbasis than some branches, such as the theory of assemblages, or the analysissitu