Rooted most deeply in the naïve consciousness of mankind is the opinion that thinking is abstract, without any concrete content; it can at most give us an "ideal" counterpart of the unity of the world, but never the unity itself. Whoever judges in this way has never made it clear to himself what a percept without the concept really is. Let us see what this world of percepts is like: a mere juxtaposition in space, a mere succession in time, a mass of unconnected details -- that is how it appears. None of the things which come and go on the stage of perception has any direct connection, that can be perceived, with any other. The world is thus a multiplicity of objects of equal value. None plays any greater part in the whole machinery of the world than any other. If it is to become clear to us that this or that fact has greater significance than another, we must consult our thinking. Were thinking not to function, the rudimentary organ of an animal which has no significance in its life would appear equal in value to the most important limb of its body. The separate facts appear in their true significance, both in themselves and for the rest of the world only when thinking spins its threads from one entity to another. This activity of thinking is one full of content. For it is only through a quite definite concrete content that I can know why the snail belongs to a lower level of organization than the lion. The mere appearance, the percept, gives me no content which could inform me as to the degree of perfection of the organization.
 Thinking offers this content to the percept, from man's world of concepts and ideas. In contrast to the content of percept which is given to us from without, the content of thinking appears inwardly. The form in which this first makes its appearance we will call intuition. Intuition is for thinking what observation is for percept. Intuition and observation are the sources of our knowledge. An observed object of the world remains unintelligible to us until we have within ourselves the corresponding intuition which adds that part of reality which is lacking in the percept. To anyone who is incapable of finding intuitions corresponding to the things, the full reality remains inaccessible. Just as the color-blind person sees only differences of brightness without any color qualities, so can the person without intuition observe only unconnected perceptual fragments.
 To explain a thing, to make it intelligible, means nothing else than to place it into the context from which it has been torn by the peculiar character of our organization as already described. A thing cut off from the world-whole does not exist. All isolating has only subjective validity for our organization. For us the universe divides itself up into above and below, before and after, cause and effect, thing and mental picture, matter and force, object and subject, etc. What appears to us in observation as separate parts becomes combined, bit by bit, through the coherent, unified world of our intuitions. By thinking we fit together again into one piece all that we have taken apart through perceiving.
 The enigmatic character of an object consists in its separateness. But this separation is our own making and can, within the world of concepts, be overcome again.