Key issues of anarchism: Various dictionaries we have consulted define spirit as an incorporeal substance, an immaterial breath that animates and activates bodies, but the word spirit (page 44 of the Anarchist Encyclopedia of Sebastian Faure) is a vague term inasmuch as the definition varies according to the philosophical doctrine . The spirit, as the word is commonly used, is, therefore, the power to conceive, to compare, to judge, to reason — and it is indeed in this sense that it is frequently used. In the eighth question posed in his “Ignorant Philosopher” Voltaire tells us: “As we can have no notion, but by experience, it is not impossible that we can ever know what matter is. We touch, we see the properties of this substance; but this very expression “substance which is beneath,” sufficiently acquaints us that this thing beneath will ever be unknown to us; whatever we may discover of its appearance, there will always remain this beneath to discover. For the same reason, we can never know by ourselves what is spirit. It is a word which usually signifies breath, and by which we endeavour to express vaguely and grossly that which gives us thoughts. But when, even by a prodigy, which is not to be supposed, we should acquire some slight idea of the substance of this spirit, we should be no farther advanced; and we could never guess how this substance received sentiments and thoughts. We know very well that we have some small intellectual faculty; but how do we obtain it? This is a secret of nature, which she has not divulged to any mortal.” If the human body is considered as consisting of chemical compounds, the spirit is the flame that comes from the body, as fire is obtained from a chemical phosphate , and briefly say that the spirit is a force born of matter, inherent in matter , and may not be the manifestation of a separate intangible power of bodily substance . To satisfy our curiosity on this issue the following study. “Key issues of Anarchism” by the late Fabian Moro examines those ideas that seek to rationalise the concept ‘spirit’.