Observation and thought are the two points of departure for all the spiritual striving of man, in so far as he is conscious of such striving. The workings of common sense, as well as the most complicated scientific researches, rest on these two fundamental pillars of our minds. Philosophers have started from various ultimate antitheses, Idea and Reality, Subject and Object, Appearance and Thing-in-itself, Ego and Non-Ego, Idea and Will, Concept and Matter, Force and Substance, the Conscious and the Unconscious. It is, however, easy to show that all these antitheses are subsequent to that between Observation and Thought, this being for man the most important. Whatever principle we choose to lay down, we must either prove that somewhere we have observed it, or we must enunciate it in the form of a clear concept which can be re-thought by any other thinker. Every philosopher who sets out to discuss his fundamental principles, must express them in conceptual form and thus use thought. He therefore indirectly admits that his activity presupposes thought. We leave open here the question whether thought or something else is the chief factor in the development of the world. But it is at any rate clear that the philosopher can gain no knowledge of this development without thought. In the occurrence of phenomena thought may play a secondary part, but it is quite certain that it plays a chief part in the construction of a theory about them. As regards observation, our need of it is due to our organisation. Our thought about a horse and the object "horse" are two things which for us have separate existences. The object is accessible to us only by means of observation. As little as we can construct a concept of a horse by mere staring at the animal, just as little are we able by mere thought to produce the corresponding object. In time observation actually precedes thought. For we become familiar with thought itself in the first instance by observation. It was essentially a description of an observation when, at the beginning of this chapter, we gave an account of how thought is kindled by an objective process and transcends the merely given. Whatever enters the circle of our experiences becomes an object of apprehension to us first through observation. All contents of sensations, all perceptions, intuitions, feelings, acts of will, dreams and fancies, images, concepts, ideas, all illusions and hallucinations, are given to us through observation.