Then energy is not in the least like matter--either the matter of science or that of philosophy. The energy we really know is a unique experience--not a general idea, nor anything analogous to a phenomenal object; so that even if the proposed precedent were true in itself, it is not applicable to the case. To complete our knowledge of external energy we must go back to that comparison which first suggested to us that there is external energy, namely, the comparison of living man with living nature. If this is not a correct account of the derivation of the notion that cosmic energy is indestructible, let conservationists tell us what is the parallel on which they are arguing. Here is a blank theorem for completion-- _x_ | is indestructible -------------------+------------------------------ Cosmic energy is a | _it must therefore be considered sort of _x_ | indestructible_ Matter, as we have seen, is not _x_. Human energy is not _x_. Our individual power--so far as experience informs us--is destroyed in the using. A day's work exhausts us, and we have to pass into the condition called sleep to be refilled. It is sleep, not food, that refreshes the mind. Food restores the bodily tool we have been working with--puts a fresh edge on the chisel,--but it does not recuperate the power that wields the tool. What then is _x_? _NOTE ON DREAMS_ If dreams could be studied with our waking consciousness they would throw much light on our mental nature. Being a poor dreamer myself I am not competent to discuss this phase of psychology as it deserves. I think however the bulk of our dreams can be reduced to two principles. There is first the simple lowering of the mental energy, which weakens the attention and dissolves the artificial categories, thus making ordinary reason impossible. There is just enough energy left to revive a few scattered ideas, which blend together without control or regard to precedent. Hence the singular combinations they sometimes form. In the waking state the objective and intellectual experience are generally more vivid and engrossing than the sentimental--at least in masculine persons. (I deliberately avoid the phrase 'masculine mind,' because there is manifestly no sex in mind.) In dreams the converse of this is the case. The objects we appear to see are dull and indistinct, being ideas mistaken for objects, whilst the feelings are evidently genuine and sometimes of great intensity. This may be explained on the occult principle alluded to in section X.