Mankind is a system of creatures, that continually need one another's assistance, without which they could not long subsist. It is therefore necessary, that everyone, according to his capacity and station, should contribute his part towards the good and preservation of the whole, and avoid whatever may be detrimental to it. For this end they are made capable of acquiring social or benevolent affections, (probably have the seeds of them implanted in their nature) with a moral sense or conscience, that approves of virtuous actions,a nd disapproves the contrary. This palinly shows them, that virtue is the law of their nature, and that it must be their duty to observe it, from whence arises moral obligation, tho' the sanctions of that law are unknown; for th econsideration of what the event of an action may be to the agent, alters not at all the rule of his duty, which is fixed in the nature of things. Thus, as St. Paul tells us, those who had not the law (the revealed law) were a law unto themselves: the obligation of living suitably to a rational and social nature was plain: the consequence was to be trusted to the author of that nature.
Catharine Trotter Cockburn, Philosophical Writings. Patricia Sheridan, ed. (Broadview: 2006), p. 114.
Catharine Trotter (1679-1749), also called Catharine Cockburn, is one of a number of early modern women writing on philosophical topics who are finally beginning to be studied. She is most famous for her defense of Locke against impiety; Locke wrote her personally to thank her. She also wrote plays from a very young age; I gave a sample from The Revolution of Sweden about two years ago. (Wow! Time certainly does fly.) This particular passage is from a set of published remarks on a controversy about the foundation of moral obligation and virtue.