Thus we have learned what Einstein regards as the sole purpose of Science, namely, the search after Truth. For him, the latter is something absolute in itself, and the possibility of getting nearer to it is as great as the impossibility of deriving results of scientific use from, say, ethical discoveries. For ethics is a field which is haunted by the conceptual ghosts, and the manner of treatment, _ordine geometrico_, that Spinoza wished to apply to it, is reserved for physics. Einstein leaves the inverse philosophical query: "Is not Truth in itself only something that we have constructed in imagination?" to those who find pleasure in sauntering along paths of thought that are totally unconnected, whereas he himself advances in a straight line with the consciousness that even if the goal is unattainable, he will at least not lose the right direction! CHAPTER VIII HIGHWAYS AND BY-WAYS Practical Aims of Science.--Pure Search for Truth.--Retrospective Considerations.--The Practical Side of Kepler.--A Saying of Kant.--Mathematics as a Criterion of Truth.--Deductive and Inductive Methods.--Conceptual and Perceptual Knowledge.--Happiness and the Pleasures of Theory.--Achievements of Science and Works of Art.--Ethical Results.--Minor Questions. AGAIN we chanced to refer to the great subject: Can or should theoretical science also pursue practical aims? It is impossible to overrate the importance of this question. It haunts us daily and often enough looms up threateningly on the horizon of mankind. Observe what form the discussions of educated people take when the finest and most sublime achievements of mind are being debated: one talks of the wonders of research in the remotest corners of astronomy where the structures of world-wide star-systems are being investigated; we hear observations about the theories that aim at tracing the cosmogonic development of universes from the original chaos of countless ages ago. We hear mention of exalted sciences, the Theory of Functions and Numbers, whose founders and representatives are just as remarkable in propounding problems as in solving them, and inevitably the following question obtrudes itself: Of what use is it, ultimately? What can one do with it? Can it be admitted that theoretical science has an object of its own, or have we at least the right to maintain the hope that, sooner or later, it will bring us a real "Utility" expressible in practical terms? And just as the devotees of pure art have framed the expression, "L'art pour l'art," so Einstein proclaims that science is its own object, "Science for its own sake!" It carries its aims absolutely in itself and must not, through aiming at other purposes, stray from its own highways. "It is my inner conviction," said he, "that the development of science itself seeks in the main to satisfy the longing for pure knowledge, which, psychologically, asserts itself as religious feeling."