“ Ignorance of the Law of Nature Excuseth no man; because every man that hath attained to the use of Reason, is supposed to know, he ought not to do to another, what he would not have done to himselfe. ”
 Thomas Hobbes, Leviathan (1651). copy citation

add

“or some errour in Reasoning, or some sudden force of the Passions. Defect in the Understanding, is Ignorance; in Reasoning, Erroneous Opinion. Again, ignorance is of three sort; of the Law, and of the Soveraign, and of the Penalty. Ignorance of the Law of Nature Excuseth no man; because every man that hath attained to the use of Reason, is supposed to know, he ought not to do to another, what he would not have done to himselfe. Therefore into what place soever a man shall come, if he do any thing contrary to that Law, it is a Crime. If a man come from the Indies hither, and perswade men here to receive a new Religion, or teach them any thing that tendeth to disobedience of the Lawes of this Country, though he be never so well perswaded of the truth of what he teacheth, he commits a Crime, and may be justly punished for the same, not onely because his doctrine is false, but also because he does that which he would not approve in another, namely, that comming from hence, he should endeavour to alter the Religion there.” source