III. “The World is my Idea”
1. Objects: Objects only exist for a subject – For a human being, “what he knows is not a sun and an earth, but only an eye that sees a sun, a hand that feels an earth; that the world which surrounds him is there only as an idea, i.e. only in relation to something else, the consciousness, which is himself.
2. Sensation: Schopenhauer speaks of the body as immediate object. The body as immediate object is sensation. The form of the body and the knowing subject cannot be known at this level. In other words, we can have sensations and know, but we cannot know objects or ourselves without some higher level of knowing, such as understanding, which can perceive objects in space and through causation.
3. Understanding: refers to the knowledge of cause and effect and the transition from cause to effect and from effect to cause. Understanding exists in al animals, although it varies considerably in degree. Laws of nature, for example gravitation, must be first grasped in the understanding. Deception of understanding is illusion.
4. Reason: is abstract knowledge embodied in concepts. Animals do no possess it. The greatest value of reason is that its knowledge can be communicated and permanently retained. Abstract reasoning, which only serves to make the immediate knowledge of the understanding permanent for thought by bringing it under abstract concepts, i.e., it makes knowledge distinct, it puts in a position to impart it and explain it to others. Speech, as a means of communicating, is the first function and a necessary prerequisite for reason. Deception of reason is error. Reason almost always acts on something given to it through sensation and understanding. Only the bare principles of identity, contradiction, excluded middle, and sufficient reason are present in pure reason alone. Although reason is necessary for some accomplishments, it is also shallower than the understanding. “The knowledge of the relation of cause and effect arrived at by the understanding, is in itself far completer, deeper and more exhaustive than anything that can be though about in the abstract; the understanding alone knows in perception directly and completely the nature of the effect of a level, of a pulley, or a cog-wheel, the stability of an arch, and so forth. But on account of the peculiarity of the knowledge of perception just referred to, that it only extends to what is immediately present, the mere understanding can never enable us to construct machines and buildings. Here reason must come in. It must substitute abstract concepts for ideas of perception and take them as the guide of action and if they are right the anticipated result will happen.” (#12)
5. Science: The special characteristic of science is not certainty but rather systematic form, that is, an ordered system with a process of subordination from general to particular (#14). Although deductive argument, demonstration is the aim of science, we should not forget that science originates in the world of perception. “In order to improve the method of mathematics, it is especially necessary to overcome the prejudice, that demonstrated truth has any superiority over what is known through perception or that logical truth founded upon the principle of contradiction has any superiority over metaphysical truth, which is immediately evident, and to which belongs the pure intuition or perception of space” (#15). Al empirical knowledge is subject to error or illusion in so far as it goes from effect to cause “for the same consequent may follow from different reasons. Since so much science goes from effect to cause “all natural philosophy rests upon hypotheses which are often false” (#15). “Only in the case of purposely arranged experience knowledge proceeds from the cause to the effect, that is, it follows from a method that affords certainty but these experiments themselves are undertaken in consequence of hypotheses” (#15).
