The analysis of any idea and the theoretical analysis of any object, or of the thing which suggested the idea, is one and the same. Every idea corresponds to some real object. Ludwig Feuerbach has demonstrated that even the concepts of God and immortality are reflections of real objects which can be perceived by the senses. For the purpose of analyzing such ideas as animal, light, friendship, man, etc., the phenomena, the objects, such as animals, friendships, men, and lights, are analyzed. The object which serves for the analysis of the concept "animal" is no more any single animal, than the object of the concept "light" is any single light. These concepts comprise classes, things in general, and therefore the question, or the analysis, of what constitutes the animal, the light, friendship, must not deal with any concrete, but with the abstract elements of the whole class.
The fact that the analysis of a concept and the analysis of its object appear as two different things is due to our faculty of being able to separate things into two parts, viz., into a practical, tangible, perceptible, concrete thing and into a theoretical mental, thinkable, general thing. The practical analysis is the premise of the theoretical analysis. The individually perceptible animals serve us as a basis for the analysis of the animal concept, the individually experienced friendships as the basis for the analysis of the concept of friendship.
Every idea corresponds to an object which may be practically separated into its component parts. To analyze a concept is equivalent, therefore, to analyzing a previously experienced object by theoretical means. The analysis of a concept consists in the understanding of the common or general faculties of the concrete parts of the analyzed object. That which is common to the various modes of walking, the rythmical motion, constitutes the concept of walking, that which is common to the various manifestations of light constitutes the concept of light. A chemical factory analyzes objects for the purpose of obtaining chemicals, while science analyzes them for the purpose of obtaining their concepts.
The special object of our analysis, the faculty of thought, is likewise distinguished from its concept. But in order to be able to analyze this concept, we must analyze the object. It cannot be analyzed chemically, for not everything is a matter of chemistry, but it may be analyzed theoretically or scientifically. As we have already stated, the science of understanding deals with all objects. But all objects which this science may wish to analyze theoretically, must first be handled practically. According to their special natures, they must either be handled in various ways, or carefully inspected, or scrutinized by intent listening, in short they must be thoroughly experienced in some way.
It is a fact of experience that men think. The object or suggestion is furnished by facts, and we then derive the concept instinctively. Thus, to analyze the faculty of thought means to find that which is common or general to the various personal and temporary processes of thought. In order to follow this study by the methods of natural science, we require neither physical instruments nor chemical reagents. The sense perception which is indispensable for every scientific understanding, is so to say present in this case a priori, without further experience. Every one possesses the object of our study, the fact of thought faculty and its experience, in the memories of himself or herself.
We have seen that thought like any other activity as well as its scientific analysis is everywhere developing the general or abstract out of particular and concrete sense perceptions. We now express this in the following words: The common feature of all separate thought-processes consists in their seeking the general character or unity which is common to all objects experienced in their manifold variety by sense perceptions. The general element which is common to the different animals, or to the different manifestations of light, is that which constitutes the general animal or light concept. The general is the nature of all concepts, of all understanding, all science, all thought processes. Thus we arrive at the understanding that the analysis of the faculty of thought reveals its nature of finding that which is general and common to concrete and distinct things. The eye studies the visible, the ear the audible, and our brain that which is generally conceivable.
We have seen that thought like any other activity requires an object; that it is unlimited in the choice of its objects, because all things may become the objects of thought; that these objects are perceived in manifold forms by various senses; and that they are transformed into simple ideas by extricating that which they possess in common, which is similar, which is general in them. If we apply this experienced understanding of the general method of thought processes to our special object, the faculty of thought, we realize that we have thus solved our problem, because all we were looking for was the general method of the thought process.
If the development of the general out of the concrete constitutes the general method by which reason arrives at understanding, then we have fully grasped reason as the faculty of deriving the general out of the concrete.
Thinking is a physical process and it cannot exist or produce anything without materials any more than any other process of labor. My thought requires some material which can be thought of. This material is furnished by the phenomena of nature and life. These are the concrete things. In claiming that the universe, or all things, may be the object of thought, we simply mean that the materials of the thought process, the objects of the mind, are infinite in quantity and quality. The materials which the universe furnishes for our thought are as infinite as space, as eternal as time, and as absolutely manifold as the nature of these two forms of being. The faculty of thought is a universal faculty in so far as it enters into relations with all things, all substances, all phenomena, and thus generates thought. But it is not absolute, since it requires for its existence and action the previous presence of matter. Matter is the boundary, beyond which the mind cannot pass. Matter furnishes the background for the illumination of the mind, but is not consumed in this illumination. Mind is a product of matter, but matter is more than a product of mind, being perceived also through the five senses and thus brought to our notice. We call real, objective products, or "things themselves" only such products as are revealed to us simultaneously by the senses and the mind.
Reason is a real thing only in so far as it is perceived by the senses. The perceptible actions of reason are revealed in the brain of man as well as in the world outside of it. For are not the effects tangible by which reason transforms nature and life? We see the successes of science with our eyes and grasp them with our hands. It is true that science or reason cannot produce such material effects out of themselves. The world of sense perceptions, the objects outside of the human brain, must be given. But what thing is there that has any effects "in itself?" In order that light may shine, that the sun may warm, and revolve in its course, there must be space and other things which may be lighted and warmed and passed. In order that my table may have color, there must be light and eyes. And everything else which my table is besides, it can be only in contact with other things. Its being is just as manifold as those various contacts or relations. In short, the world consists only in its interrelations. Any thing that is torn out of its relations with the world ceases to exist. A thing is anything "in itself" only because it is something for other things, by acting or appearing in connection with something else.