XLIII. Not only with regard to the angels, but on the part of brutes also, we find motives for doubting, whether the definition of _rational animal_, may not be applied to them as well as to man. If _rational animal_ signifies an animal capable of reflexion, the brutes are rational animals in the opinion of all those, who suppose them to be endowed with reason and reflexion: and as this sentiment may be supported by strong arguments, it remains somewhat doubtful, whether rationality is not diffused in different proportions to other animals as well as men, or whether it is confined to them only. It is true, that if this opinion should be admitted, we should grant, that the reason of man is distinct from, and of a superior nature to that of brutes; but if in the definition, we do not point out the character which distinguishes them, we are reduced to assign as the difference, a generical idea. SECT. X. XLIV. As we ascend the predicamental tree, and advance from the species, to the genuses or kinds; we perceive, that philosophy does not discern these more clearly, than it did the others; for we find in both cases, equal ignorance, and equal uncertainty. If we ought to have scientific certainty of any one genus in preference to another, it should be of that under which we ourselves are comprehended, which is the animal kind, for that is the thing which most immediately relates to us, and because also, we employ more consideration and attention upon that, than we do upon the others. We call the order animal, which comprehends man, and every other species of terrestrial and aquatic brutes, as likewise every kind of fish or fowl. And what do we know of animals according to this general description? Why that they are _sensitive living beings_; for that is the definition we give of them. But do we know this with any degree of certainty? By no means; for it has been doubted whether every animal is sensitive; and it has also been doubted, whether the sense of feeling does not belong to other entities as well as to animals.