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in receiving light or as a sheet of paper in receiving marks.
It has become evident that the mind is not only passive in perception, but is also active; that its activity is far too important to be ignored or questioned; that it receives no knowledge of external things from them, but produces its knowledge of them by its own action; that it supplies from its own internal sources alone all the materials of percepts, and constructs percepts by its own unifying efficiency. But in the recognition of the generative and constructive activity of mind in the formation of percepts or the cognitive modes, there should be the most decided shunning of the prime aberration of the idealists in their postulation that the activity of the mind in perception is wholly uninfluenced by outside objects, as there are no outside objects to influence it; that the only objects are the internal percepts or subject-objects, which have no possible relation with real external things and can in no degree or manner represent them. Realism contends, on the contrary, that though the mind is to so considerable an extent active in perception, it is also to a very real extent dependent and passive; that while percepts, or representations of external realities, are entirely constructed by the mind from materials furnished by the mind itself, yet the construction is initiated and controlled by the influence of the realities; that percepts represent objects of particular shapes, sizes, times, motions, forces, not of its own arbitrary purpose and perfectly self-originated and independent activity, but because real outer objects possessing these particular qualities influence the mind by them in the formation of the percepts. Thus it is
held that while the mind is so largely active in knowing external objects, the objects also are active upon the mind in being known.
Again, realism has come to see itself under the necessity of admitting that it is not a satisfactory and sufficient theory and proof of the existence of extramental objects, to claim a belief in the existence of such objects that is natural and necessary, that will not permit the negation of itself, that cannot be expelled. This proof is conceived to be in itself inadequate, and has been abandoned by many. But certainly an irresistible belief in external objects universally exists, and is a very remarkable fact. Idealists are compelled to consider it; but their attempts to account for it have been ignominious failures. The belief always demands capabilities and processes of knowledge which they do not recognize. Realists however feel that they cannot stop with an appeal to this belief, certain and potent as it is; but are under obligation to go on and give some account of the rise, development and worth of the belief; or to show, in the character and processes of our senses and the ordinary operations of our intellect, the possibility of apprehending, or forming true and binding inferences and representations of, external realities.
THE NATURE AND OUR PERCEPTION OF MATTER
In the preceding chapter we have given some consideration to Object-Objects in general; now we come to treat of a particular Object-Object, that is, Matter. According to the more common understanding, matter is an extended, inanimate, inert and permanent reality entirely independent of our mind or thought.
The scientific discussions of the nature of matter have long had particular regard to the questions of the divisibility of matter and the character and relation of its ultimate elements. Metaphysicians have ardently debated whether matter is infinitely divisible or whether there is a limit to division. They have agreed that though both alternatives are inconceivable, yet one of them must be true.
We are perfectly familiar with the divisibility of the tangible material objects that we constantly encounter, as pieces of wood, lumps of earth, stone. We may break a stone into pieces, and then break any one of these pieces into smaller, and so on, until we can divide no farther or not into perceivable fragments. When partition ceases to be practicable, we may carry it on many stages mentally and by aid of mathematical symbols. The ideal division of matter is related to what is called the "theoretical construction" of matter. It is common to postulate the ideal division as continued down to very minute particles called atoms.
These are conceived to be separated from one another by empty spaces, and to be held in equilibrium (even with changing collocation) by their inherent attractive and repulsive forces. By elements so related, it is supposed, are constituted the tangible masses, the ordinary material objects, we meet with. The objects seem to us to be perfectly continuous and solid because our senses are not acute enough to discriminate the constituent elements and the void spaces that separate them.
What the substance or nature is of the so called atoms, or of the conjectured atoms of atoms, is a subject concerning which physicists confess the greatest uncertainty. It is generally believed to be impossible to tell whether they are electrical, or ethereal, or of some other character; but future research may solve the mystery. It is strange to be compelled to admit that objects, which seem so well known and so real, are thus as to their constituents unknown.
Respecting the question whether matter is infinitely divisible, whether the atoms themselves are divisible into subordinate atoms, and these again divisible into fragments, and so on, some metaphysicians seem to hold that, as we can think, or speak understandingly, of the infinite divisibility of matter, therefore it must be possible, or it could be effected if a sufficient force could be applied. This would seem to involve the possibility of dividing matter to nothingness, or to unextended elements. Something similar to this wholly unfounded and perverse presumption of a real divisibility corresponding to a divisibility verbally predicable, metaphysicians have endeavored to maintain respecting space. It seems unreasonable to suppose that the last elements of matter are unextended;
because of the manifest impossibility of unextended elements constituting the extended objects we certainly know. Any number of unextended units cannot make up an extended thing.
The theory has been deliberately propounded that the ultimate units of matter are unextended, or but punctual, centres of force-of pure force free from any substance or substratum. But the impossibility of any multitude of such unextended centres composing any of the masses of matter which we are constantly and clearly perceiving, is fatal to the theory. The theory is entitled to consideration only upon the supposition that the conjectural centres of force are separated from one another by real void spaces, and are maintained in equilibrium by their mutual attractions and repulsions. According to this view, a piece of matter is a multitudinous group of centres of force severed from one another, and firmly balanced, in real space, and thus as a group possessing real and perceivable extension and offering resistance.
The ideal division of matter into infinitesimal, absolutely imperceivable particles, has led to some sceptical surmisings and assumptions as to the reality and cognizability of any sort or form of matter. Some have doubted and denied the reality of atoms, declaring them to be only ideal.1 Some have been led by
1“These supposed actualities [mass-points, atoms], behind what can possibly be seen or felt, are not only not absolute realities, they are not even phenomenal realities; they are simply conceptions which the physicist has reached by idealizing what he can see and feel; thoughts not things, ideas existing solely for the minds of physicists." (Ward, Naturalism and Agnosticism, II. 102.)
"Natural science considers the world as a mechanism, and for that purpose transforms the reality in a most complicated and ingenious way. It puts in the place of the perceivable objects unperceivable atoms which are merely products of mathematical construction quite unlike any known thing." (Münsterberg, Psychology and Life, p. 20.)