In what does man's pre-eminence over the brute creation consist? The answer is as clear as that a half is less than the whole, in Reason.
What acquirement exalts one being above another? Virtue, we spontaneously reply.
For what purpose were the passions implanted? That man by struggling with them might attain a degree of knowledge denied to the brutes, whispers Experience.
Consequently the perfection of our nature and capability of happiness must be estimated by the degree of reason, virtue, and knowledge, that distinguish the individual, and direct the laws which bind society: and that from the exercise of reason, knowledge, and virtue naturally flow, is equally undeniable, if mankind be viewed collectively.
The rights and duties of man thus simplified, it seems almost impertinent to attempt to illustrate truths that appear so incontrovertible; yet such deeply rooted prejudices have clouded reason, and such spurious qualities have assumed the name of virtues, that it is necessary to pursue the course of reason as it has been perplexed and involved in error, by various adventitious circumstances, comparing the simple axiom with casual deviations.
--Mary Wollstonecraft, A Vindication of the Rights of Women (1792), Part I, Chapter I. I've always liked this passage.