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.)

the conceptual divisibility of tangible masses, the masses with which division is supposed to begin, to doubt and deny the reality of the masses themselves; and to consider them as wholly ideal, or as only appearances, or as things that vanish by partition. It has been said that matter is entirely "unknowable," that "matter however conceived by us cannot be matter as it actually is." An eminent physicist has asserted that "we do not know and are probably incapable of discovering what matter is."

Atoms may be held to be real, and not only ideal, because they are attained by a division of tangible and perceivable masses. They are reached by the mental continuation of a division which may be actually carried to a distance unto fragments that are perceivable. We come to them by a justifiable process of inference from real and definitely knowable masses. Then, though they are ideal, they are in this wise also real.

The declarations, that we know not what matter is, that it is quite incognizable, that matter as conceived by us cannot be matter as it exists, and the like, are far too sweeping and indiscriminating. It must be conceded at once that we know not the ultimate constituents of matter, whether they are electrical corpuscles, whirls of ether, or something else; in respect to these, matter is certainly unknown. But matter as composed of the conjectural constituents, that is, the common material objects of our perception,-sticks of wood, stone, rods and balls of metal,-are indisputably known as to their extension, extension including figure and magnitude. The material object, entirely unknown as respects its ultimate elements and structure, 1 Spencer, First Principles, p. 94.

is yet clearly and certainly known as respects the form and size of its mass.

The object may be compounded of elements whose distances from one another are very many times longer than the diameter of the elements themselves; but the distances are yet very short for us, being undiscernible by our sharpest sensibility. As consisting of a collection of such severed, but for us very close, elements, held strongly in equipoise, the object has real extension, real stable figure and size, which are known by us as they are. To this extent matter is truly knowable, is represented by us as it exists. In such a manner we would contend for the duty of holding on to the knowableness and reality of the ordinary material objects of our perceptions, against every mode of the "theoretical construction" of matter that denies or is inclined to deny these facts. We must not allow ourselves to be beguiled out of them by any sort of metaphysical sophistication. The ideal construction of the interior of matter, so to speak, must always maintain itself in consistency with matter as we perceive it in its extension or in its shape and magnitude. The extended perceivable objects carry in themselves, in their own being, the decisive proof that their ultimate constituents cannot be unextended. Finally, it should be remarked and accentuated that the knowledge of the figure and magnitude of material objects is not an insignificant knowledge, but forms a very large and important part of all the knowledge of matter contended for by any sect of metaphysicians.

These considerations bring us directly to the supreme question, How do we come to know especially the extension of material realities? Let us then, dismissing

now every other question, proceed to wrestle with this paramount problem. It is proposed to treat this great problem of cognition with particular reference to the Berkeleian immaterialism. This mode of procedure seems advisable, because the great influence of Berkeley upon present-day idealism and monism is unmistakable. The strongest argumentation in our time against the matter of dualistic or natural realism is largely drawn from Berkeley. We meet in current idealistic literature frequent echoes of Berkeley such as these: "All matter is given to us only as idea in our consciousness"-"To talk about knowing the external world through ideas which are merely within us, is to talk of an inherent self-contradiction”—“A world external to and independent of the mind would for us be forever inaccessible"-"It would be impossible to compare the internal idea with the external object."

But, first, since the theory of Berkeley took its start from Locke's philosophy of the reality and cognizability of external bodies, and was developed in opposition to its main tenets, brief preliminary attention to the doctrine of Locke will furnish important help to the understanding of the teaching of Berkeley, will get valuable light upon its course and conclusions.

Locke was a dualistic realist of the Cartesian type, holding to matter as an extended substance distinct from and independent of the substance of mind. As to knowledge, and first as to knowledge in general, he maintained that the only objects of immediate knowledge are our ideas; that of matter and all external things our knowledge is only inferential or mediate. The media of the knowledge of external realities are our immediately or intuitively known ideas. He says: "The mind, in all its thoughts and reasonings, hath