There is another principle to which our author attaches, as we think, too little importance in this connection. When we see how vast is the variety of organic beings on this globe, and how manifold the conditions of their existence; how exactly adapted they are to the solid, the liquid, and the gaseous states of matter, can we doubt that rational and intelligent beings may be adapted to physical conditions in other worlds widely diverse from those on this globe? May not spirits be connected with bodies much heavier, or much lighter, than on earth; nay, with mere tenuous ether; and those bodies, perhaps, be better adapted to the play of intellect than ours; and be unaffected by temperatures which, on earth, would be fatal? It does seem to us that such conclusions are legitimate inferences from the facts of science; and if so, we can hardly avoid the conclusion that there may be races of intelligent beings upon other worlds where the condition of things is widely different from that on earth. Yet there is a limit to this principle; and when we can prove another world to be in a similar condition to our earth, when it was inhabited by preadamic races, or not at all inhabited, the presumption is strong, that such a world has inhabitants of a like character, or none at all. Our author makes but a slight allusion to some most important statements of revelation, that seem to us to bear strongly upon the hypothesis which he adopts. We refer to the existence of angels, holy and unholy. In the history of the latter, we learn that _they kept not their first estate, but left their own habitation_. Have we not here an example of other rational creatures, more exalted than man, who, like him, have fallen from their first estate; and does not the presumption hence arise, that there may be similar examples in other worlds? And is there not a probability, that holy angels now in heaven, may be rational intelligences who have passed a successful probation in other worlds? It does seem to us, that these biblical facts make the hypothesis of our author respecting man extremely improbable.