Now, in the first place, they have always been thought of as pure spiritual beings, having no such gross terrestrial body as man has. At least, if they were supposed to require and possess a body as the organ and medium of their spiritual operations, it was considered to be of a special kind--an ethereal body of light, but invisible to the human eye. But this incorporeity is little more than a negative quality. A more positive and a profounder distinction lies perhaps in this, that these pure spiritual beings are wholly free from that weakness of character, or frailty, which is so peculiar to man. That pervading internal mutability, that undecided vacillation between doing and letting alone, that reciprocation between effort and relaxation--the wide gulf between volition and execution, the thought and the carrying into effect--nothing of all this admits of being applied or transferred to these pure spiritual beings without contradicting the very idea of their essence. It is thus only, or not at all, that we can conceive of them. Coming and going like the lightning, and rapid as the light, they never grow weary of their endless activity. They need no rest, except the spiritual contemplation which constitutes their essence. All their thoughts are marked with unity and identity. With them the conception is at the same time a deed, and the purpose and the execution are simultaneous. Every thing, too, in them has the stamp of eternity. This prerogative, however, has, it must be confessed, its disadvantages. When once they have deviated from the true center, they go on forever in their devious course.