_Answ._ The heart is so deceitful that you have great cause to watch, lest human frailty be pretended, for that error, which a corrupted, biassed, partial mind, or wilful laziness, is the cause of. Diligent study, and inquiry, and prayer, with a sincere desire to know the truth, may succeed, at least, to so much satisfaction, as may keep your minds in quietness and peace, and give you comfort in your way, and preserve you from all such sin as is inconsistent with this your safety and acceptance with God. But yet it is true that human frailty will occasion in the best uncertainties in some particular cases; and though God make it not our duty of two sins to choose the less, but to refuse both, yet he maketh it our duty more diligently to avoid the greater than the less. And ofttimes the case is so sudden that no inquiry can be made: and therefore I confess a christian should know which sins are greatest and to be most avoided. At present I shall lay down these following rules, premising this, that where accidents and circumstances which make sins great or small are to be compared, they are ofttimes so numerous and various, that no rules can be laid down beforehand, that will serve all turns, no more than in law and physic, any law books or physic books will serve all cases without a present experienced judicious counsellor: present prudence and sincerity must do most.
_Rule_ I. In things altogether indifferent, nothing must be done that conscience doubteth of, because there is a possibility or fear of sinning on the one side, but none on the other; and in that case it is a certain sin to venture on a feared sin. But then it is supposed that the thing be indifferent as clothed with all its circumstances, and that there be no accident that taketh away its indifferency.
_Rule_ II. In case the thing be really unlawful, and I think it to be lawful, but with some doubting, but am clear that the forbearing it is no sin; there the sin is only in the doing it; because all is clear and safe on the other side.
_Rule_ III. There are many sins which are always and to all persons in all cases sins, and not doubted of by any without gross unfaithfulness or negligence; and here there is no room for any doubting whether we must do that good which cannot be done without that sin, it being certain that no such good can be a duty. As, to commit idolatry, to blaspheme God, to deny Christ, to deny the Scriptures, to hate, or reproach, or oppose a holy life, to be perjured, to approve or justify the sin of others, &c. It can be no duty which cannot be done without the wilful yielding to or committing these or any known sin.
_Rule_ IV. There are some duties so great, and clear, and constant to all, that none but a profligate or graceless conscience (or one that is fearfully poisoned with sin) can make a doubt of it deliberately: these therefore come not within the case before us.
_Rule_ V. If moral evil be compared only with natural good, or moral good with natural evil, there is no doubt to be made of the case: the least sin having more evil in it than the prosperity or lives of millions of men have good (considered in themselves as natural good); and the least duty to God having more good in it than the death of millions of men (as such) hath evil. For the good of duty and the evil of sin are greatened by their respect to God, and the other lessened as being good or evil only unto men, and with respect to them.