The commonplace and inept knowledge differs from the most exalted, rarest, and newly discovered science in the same way in which a petty and childish superstition differs from the historical superstition of a whole period. For this reason we may well choose our illustrations from our daily circle, instead of looking for them in the so-called higher regions of a remote science. Human common sense had long practiced the investigation of causes by inductive and scientific methods, before science realized that it would have to pursue its higher aims in the same way. Common sense does arrive at the faith in a mysterious cause of speculative reason, just like the naturalist, as soon as it leaves the field of its immediate environment. In order to stand firmly on the ground of real science, every one requires the understanding of the manner in which inductive reason investigates its causes.
To this end let us glance briefly at the outcome of the study of the nature of reason. We know that the faculty of understanding is not a "thing in and by itself," because it becomes real only in contact with some object. But whatever we know of any object, is known not alone through the object, but also through the faculty of reason. Consciousness, like all other being, is relative. Understanding is contact with a variety of objects. To knowledge there is attached distinction, subject and object, variety in unity. Thus things become mutual causes and mutual effects. The entire world of phenomena, of which thought is but a part, a form, is an absolute circle, in which the beginning and end is everywhere and nowhere, in which everything is at the same time essence and semblance, cause and effect, general and concrete. Just as all nature is in the last instance one sole general unity, in view of which all other unities become a multitude, so this same nature, or objectivity, or world of sense perceptions, or whatever else we may call the sum of all phenomena or effects, is the final cause of all things, compared to which all other causes become effects. But we must remember that this cause of all causes is only the sum of all effects, not a transcendental or superior being. Every cause has its effect, every effect causes something.
A cause cannot be physically separated from its effect any more than the visible can be separated from the eye, the taste from the tongue, in brief the general from the concrete. Nevertheless, the faculty of thought may separate the one from the other. We must keep in mind that this separation is a mere formality of thought, although it is a formality which is necessary in order to be reasonable or conscious, in order to act scientifically. The practice of understanding, or scientific practice, derives the concrete from the general, the natural things from nature. But whoever has been behind the scenes, and has looked at the faculty of thought at work, knows that, conversely the general is derived from the concrete, the concept of nature from natural things. The theory of understanding or science teaches us that the antecedent is understood by its consequent, the cause by its effect, while our practical understanding regards the after as a consequence of the before, the effect as a result of the cause. The faculty of understanding, the organ of generalization, regards its opposite, the concrete, as secondary, while the faculty of thought which understands itself regards it as primary. However, the practice of understanding is not to be changed by its theory, nor can it be; the theory intends simply to render the steps of consciousness firm. The scientific farmer differs from the practical farmer, not because he employs theory and method, for both do that, but because he understands the theory, while the practical man theorizes instinctively.
To continue: From a given multitude of facts, reason generates truth in general, and out of a succession of forms and transformations it abstracts the true cause, just as absolute multiplicity is the nature of space, so absolute variability is the nature of time. Every particle of time and space is new, original, and has never been there before. The faculty of thought enables us to find our way through this absolute medley by abstracting general concepts out of the multitude of things in space, and tracing the variations of time to general causes. The entire nature of reason consists in generalizing sense perceptions, in abstracting the common elements out of concrete things. Whoever does not fully understand reason by understanding that it is the organ of generalization forgets that understanding requires an object which must remain something outside of its conception, since such object cannot be dissolved by its conception. The being of the reasoning faculty cannot be understood any more than being in general. Or rather, being is understood when we take it in its generality. Not being itself, but the general element of being, is understood by the faculty of thought.
Let us realize, for instance, the process which takes place when reason understands something it did not know before. Think of some peculiar, unexpected and unknown chemical transformation which takes place suddenly and without apparent cause in some mixture. Assume furthermore that the same reaction takes place more frequently after that, until experience demonstrates that this inexplicable change occurs whenever sunlight touches the mixture. This already constitutes a certain understanding of the process. Assume furthermore that subsequent experience teaches us that several other substances have the faculty of producing the same reaction in connection with sunlight. We have then arranged the new reaction in line with a number of phenomena of the same class, that is to say we have enlarged, deepened, completed our understanding of it still more. And if we finally discover that a special part of the sunlight unites with a special element of the mixture and thereby produces this new reaction, we have generalized this experience, or experienced this generalization, in a "pure" state, in other words, the theory of this reaction is complete, reason has solved its problem, and yet it has done nothing more than it did when it classified the animal and vegetable kingdoms in families, genera, species, etc. To find the species, the genus, the sex, etc., of anything means to understand it.
Reason proceeds in the same way when it investigates the causes of certain transformations. Causes are, in the last instance, not noticed and furnished by means of sight, hearing, feeling, not by means of the sense perceptions. They are rather supplied by the faculty of thought. It is true, causes are not the "pure" products of the faculty of thought, but are produced by it in connection with sense perceptions and their material objects. This raw material gives the objective existence to the causes produced by the mind. Just as we demand that a truth should be the truth about some objective phenomenon, so we also demand that a cause should be real, that it should be the cause of some objective effect.
The understanding of any concrete cause is conditioned on the empirical study of its material, while the understanding of any general cause is based on the study of the faculty of reason. In the understanding of concrete causes, the material of study varies, but reason maintains a constant or general attitude. The cause, as a general cause, is a pure conception, and it is based on the study of the multiformity of concrete understandings of causes, or on the multiplied study of concrete causes. Hence we are compelled to return to the concrete material of the general concept, to the understanding of concrete causes, if we wish to analyze the concept of a general cause.
When a stone falls into the water and causes ripples on the surface, the stone is no more the cause of the ripples than the liquid condition of the water. If the stone falls on solid substances, it causes no ripples. It is the contact of the falling stone with liquid substances which causes the ripples. The cause is itself an effect, and the effect, the ripples, become a cause when they carry a piece of cork ashore. But in either case the cause is based on a mutual effect, on the interaction of the waves with the light condition of the cork.
A stone falling into the water is not a cause "in itself," not a cause in general. We arrive at such a cause only, when the faculty of thought uses concrete causes for its raw material and constructs out of them the "pure" concept of the cause in general. A stone falling into the water is only the cause of the subsequent ripples, and it becomes a general cause only through the experience that ripples always follow the falling of a stone into water.
We call cause that which generally precedes a certain manifestation, and effect that which generally follows it. We refer to the stone as the cause of ripples merely because we know that it always causes them when falling into water. But since ripples sometimes appear without being preceded by the fall of a stone, ripples have another general cause. So far as there is anything general in ripples which precedes them, it is the elasticity of the water itself which is the general cause of ripples. Circular ripples, which are a special form of ripples, are generally preceded by the falling of some body into the water, and this body is then considered as their cause. The cause is always different in proportion and to the extent of the phenomena under consideration.