1. The question _de esse_ must first be resolved, before the question of knowing or opinion. Either the thing is really lawful which is doubted of, or denied, or it is not. If it be not, then it is a sin to swear or promise to it; and here there is no case of error. But if it be really lawful, and the vowing of it lawful, then the obligations that lie upon this man are these, and in this order: (1.) To have a humble suspicion of his own understanding. (2.) To search, and learn, and use all means to discern it to be what it is. (3.) In the use of these means to acknowledge the truth. (4.) And then to promise and obey accordingly. Now this being his duty, and the order of his duty, you cannot say that he is not obliged to any one part of it, though he be obliged to do it all in this order, and therefore not to do the last first, without the former: for though you question an hundred times, What shall he do as long as he cannot see the truth? the law of God is still the same; and his error doth not disoblige him: _Nemini debetur commodum ex sua culpa_. So many of these acts as he omitteth, so much he sinneth. It is his sin if he obey not the magistrate; and it is his sin that he misjudgeth of the thing; and his sin that he doth not follow the use of the means till he be informed. So that his erring conscience entangleth him in a necessity of sinning; but disobligeth him not at all from his obedience. 2. But yet this is certain, that in such a case, he that will swear because man biddeth him, when he taketh it to be false, is a perjured, profane despiser of God; but he that forbeareth to swear for fear of sinning against God, is guilty only of a pardonable, involuntary weakness.