How shall I act rightly and wisely? This is the problem which faces every man. Hence philosophy not only teaches a way of thought but also a way of action. This is inevitably so because, unlike mysticism, it is concerned not merely with a segment of life but with the whole of it. There is something defective about a teaching if it forgets the ultimate purpose for which it itself exists, if it leaves its followers in the air, and therefore cannot be successfully applied in practical action. We may understand the value of our intellectual formulations only when they are put to the test in actual practice. In putting an idea, a theory, or a doctrine to the practical test or in bringing a way of living into practical operation, we enable it to reveal its truth or falsity, its scope or limitations, its merits or demerits. A doctrine must be tested not only by its intellectual soundness but also by its practical results. The first test can be instantly applied but the second only after a certain time has elapsed. Thus the good is separated from the bad, the right is distinguished from the wrong, the true is divided from the false, either by intelligence in the sphere of abstract ideas or by time in the sphere of spatial things. The first shoots of wheat and weeds cannot be distinguished by ordinary sight or knowledge, but give them time to grow up to maturity and everybody can distinguish them. The barrenness or fruitfulness of any teaching is in the end inexorably ascertained by applying the test of historical results, that is, the test of time.
-- Notebooks Category 20: What Is Philosophy? > Chapter 1 : Toward Defining Philosophy > # 349
