There is no way of judging how far we may depend upon the actions of men, otherwise than by knowing the motives, and grounds, and causes of them; and, if the motives of our actions be not resolved and determined into the law of God, they will be precarious and uncertain, and liable to perpetual changes.  I will shew you what I mean, by an example:  Suppose a man thinks it his duty to obey his parents, because reason tells him so, because he is obliged by gratitude, and because the laws of his country command him to do so; but, if he stops here, his parents can have no lasting security; for an occasion may happen, wherein it may be extremely his interest to be disobedient, and where the laws of the land can lay no hold upon him:  therefore, before such a man can safely be trusted, he must proceed farther, and consider, that his reason is the gift of God; that God commanded him to be obedient to the laws, and did moreover in a particular manner enjoin him to be dutiful to his parents; after which, if he lays due weight upon those considerations, he will probably continue in his duty to the end of his life:  Because no earthly interest can ever come in competition to balance the danger of offending his Creator, or the happiness of pleasing him.  And of all this his conscience will certainly inform him, if he hath any regard to religion.

Secondly: Fear and hope are the two greatest natural motives of all men’s actions:  But, neither of these passions will ever put us in the way of virtue, unless they be directed by conscience.  For although virtuous men do sometimes accidentally make their way to preferment, yet the world is so corrupted, that no man can reasonably hope to be rewarded in it, merely upon account of his virtue.  And consequently, the fear of punishment in this life will preserve men from very few vices, since some of the blackest and basest do often prove the surest steps to favour; such as ingratitude, hypocrisy, treachery, malice, subornation, atheism, and many more which human laws do little concern themselves about.  But when conscience placeth before us the hopes of everlasting happiness, and the fears of everlasting misery, as the reward and punishment of our good or evil actions, our reason can find no way to avoid the force of such an argument, otherwise than by running into infidelity.

Lastly:  Conscience will direct us to love God, and to put our whole trust and confidence in him.  Our love of God will inspire us with a detestation for sin, as what is of all things most contrary to his divine nature; and if we have an entire confidence in him, that will enable us to subdue and despise all the allurements of the world.

It may here be objected, if conscience be so sure a director to us Christians in the conduct of our lives, how comes it to pass, that the ancient heathens, who had no other lights but those of nature and reason, should so far exceed us in all manner of virtue, as plainly appears by many examples they have left on record?