Electrical, Magnetic and Optical Properties of Condensed Matter

Matter is substance that may be perceived through the medium of the senses. It has form, colour, weight, taste, smell; is hard or soft, moveable, or immoveable. Those who are acquainted with the principles of Natural Philosophy, will perceive that some of these properties are inherent in matter, and that others depend on circumstances. The human body is a material substance; that is, it has the properties of matter—so has a stone or a rock.

Whilst Copernicus has persuaded us to believe, contrary to all the senses, that the earth does not stand fast Boscovich has taught us to abjure the belief in the last thing that stood fast of the earth—the belief in "substance," in "matter," in the earth-residuum, and particle-atom: it is the greatest triumph over the senses that has hitherto been gained on earth. One must, however, go still further, and also declare war... against the "atomistic requirements" which still lead a dangerous after-life in places where no one suspects them, like the more celebrated "metaphysical requirements": one must also above all give the finishing stroke to that other and more portentous atomism which Christianity has taught best and longest, the soul-atomism. Let it be pemitted to designate by this expression the belief which regards the soul as something indestructible, eternal, indivisible, as a monad, as an atomon : this belief ought to be expelled from science!

Of course, we must avoid postulating a new element for each new phenomenon. But an equally serious mistake is to admit into the theory only those elements which can now be observed. For the purpose of a theory is not only to correlate the results of observations that we already know how to make, but also to suggest the need for new kinds of observations and to predict their results. In fact, the better a theory is able to suggest the need for new kinds of observations and to predict their results correctly, the more confidence we have that this theory is likely to be good representation of the actual properties of matter and not simply an empirical system especially chosen in such a way as to correlate a group of already known facts.