immeasurably minute fraction of existing matter? and it is answered, I find that man occupies only an immeasurably minute fraction of elapsed time: and this is, to me, an answer to the “_How_,” as concluding improbability. _How_ is balanced against _How_: Difficulty against difficulty: they neutralise each other, and leave the great question, the great reality, standing as it did before either was suggested, to be dealt with according to such evidence as God has vouchsafed us. We, therefore, do not see that the Essayist is driven to say, as Sir David Brewster alleges he is, either that because man has occupied only an atom of space, he must live only an atom of time on the earth;[66] or that because he has lived only an atom of time, he must occupy but an atom of space. In dismissing this leading portion of the Essayist’s reasonings, we shall say only that we consider it worthy of the attention of all persons occupied in speculations of this nature, as calculated to suggest trains of novel, profitable, and deeply interesting reflection. Thus far the Essayist, as followed by his opponent, on the assumption that the other bodies of the universe are fitted, equally with the earth, to be the abodes of life. _But are they?_ Here we are brought to the last stage of the Essayist’s speculations—What physical EVIDENCE have we that the other bodies of the Solar System, besides the Earth, the Fixed Stars, and the Nebulæ, are structures capable of supporting human life, of being inhabited by Rational and Moral Beings? The great question, in its physical aspect, is now fully before us: Is there that analogy on which the pluralist relies? For the existence of Life several conditions must concur; and any of these failing, life, so far as we know anything about it, is impossible. Not air, only, and moisture, but a certain temperature, neither too hot nor too cold, and a certain consistence, on which the living frame can rest. Without the other conditions, an atmosphere alone does not make life possible; still less, prove its existence. A globe of red-hot metal, or of solid ice, however well provided with an atmosphere, could not be inhabited, so far as we can conceive. The old maxim of the logicians is true: that it requires _all_ the conditions to establish the affirmative, but that the negative of any _one_ proves the _negative_. First, as to the smallest tenants of our system, the thirty[67] planetoids, some of which are certainly no larger than Mont Blanc.