It is a principle recognised not only by our own but by other legal systems that ignorance of the law is no excuse for breaking it. Ignorantia juris neminem excusat. The rule is also expressed in the form of a legal presumption that every one knows the law. The rule is absolute, and the presumption irrebuttable. No diligence of inquiry will avail against it; no inevitable ignorance or error will serve for justification. Whenever a man is thus held accountable for breaking a law which he did not know, and which he could not by due care have acquired a knowledge of, the case is one of absolute liability.
The reasons rendered for this somewhat rigorous principle are three in number. In the first place the law is in legal theory definite and knowable; it is the duty of every man to know that part of it which concerns him; therefore innocent and inevitable ignorance of the law is impossible. Men are conclusively presumed to know the law, and are dealt with as if they did know it, because they can and ought to know it.
In the second place, even if invincible ignorance of the law is in fact possible, the evidential difficulties in the way of the judicial recognition of such ignorance are insuperable, and for the sake of any benefit derivable therefrom it is not advisable to weaken the administration of justice by making liability dependent on well-nigh inscrutable conditions touching knowledge or means of knowledge of the law. Who can say of any man whether he knew the law, or whether during the course of his past life he had an opportunity of acquiring a knowledge of it by the exercise of due diligence?
Thirdly and lastly, the law is in most instances derived from and in harmony with the rules of natural justice. It is a public declaration by the state of its intention to maintain by force those principles of right and wrong which have already a secure place in the moral consciousness of men. The common law is in great part nothing more than common honesty and common sense. Therefore although a man may be ignorant that he is breaking the law, he knows very well in most cases that he is breaking the rule of right. If not to his knowledge lawless, he is at least dishonest and unjust. He has little ground of complaint, therefore, if the law refuses to recognise his ignorance as an excuse, and deals with him according to his moral deserts. He who goes about to harm others when he believes that he can do so within the limits of the law, may justly be required by the law to know those limits at his peril. This is not a form of activity that need be encouraged by any scrupulous insistence on the formal conditions of legal responsibility.
It must be admitted, however, that while each of these considerations is valid and weighty, they do not constitute an altogether sufficient basis for so stringent and severe a rule.[[382]] None of them goes the full length of the rule. That the law is knowable throughout by all whom it concerns is an ideal rather than a fact in any system as indefinite and mutable as our own. That it is impossible to distinguish invincible from negligent ignorance of the law is by no means wholly true. It may be doubted whether this inquiry is materially more difficult than many which courts of justice undertake without hesitation. That he who breaks the law of the land disregards at the same time the principles of justice and honesty is in many instances far from the truth. In a complex legal system a man requires other guidance than that of common sense and a good conscience. The fact seems to be that the rule in question, while in general sound, does not in its full extent and uncompromising rigidity admit of any sufficient justification.
§ 147. Mistake of Fact.
In respect of the influence of ignorance or error upon legal liability we have inherited from Roman law a familiar distinction between law and fact. By reason of his ignorance of the law no man will be excused, but it is commonly said that inevitable ignorance of fact is a good defence.[[383]] This, however, is far from an accurate statement of English law. It is much more nearly correct to say that mistake of fact is an excuse only within the sphere of the criminal law, while in the civil law responsibility is commonly absolute in this respect. So far as civil liability is concerned, it is a general principle of our law that he who intentionally interferes with the person, property, reputation, or other rightful interests of another does so at his peril, and will not be heard to allege that he believed in good faith and on reasonable grounds in the existence of some circumstance which justified his act. If I trespass upon another man’s land, it is no defence to me that I believed it on good grounds to be my own. If in absolute innocence and under an inevitable mistake of fact I meddle with another’s goods, I am liable for all loss incurred by the true owner.[[384]] If, intending to arrest A., I arrest B. by mistake instead, I am absolutely liable to him notwithstanding the greatest care taken by me to ascertain his identity. If I falsely but innocently make a defamatory statement about another, I am liable to him however careful I may have been to ascertain the truth. There are, indeed, exceptions to this rule of absolute civil liability for mistake of fact, but they are not of such number or importance as to cast any doubt on the validity of the general principle.
In the criminal law, on the other hand, the matter is otherwise, and it is here that the contrast between mistake of law and mistake of fact finds its true application. Absolute criminal responsibility for a mistake of fact is quite exceptional. An instance of it is the liability of him who abducts a girl under the legal age of consent. Inevitable mistake as to her age is no defence; he must take the risk.[[385]]
A word may be said as to the historical origin of this failure of English law to recognise inevitable mistake as a ground of exemption from civil liability. Ancient modes of procedure and proof were not adapted for inquiries into mental conditions. By the practical difficulties of proof early law was driven to attach exclusive importance to overt acts. The subjective elements of wrongdoing were largely beyond proof or knowledge, and were therefore disregarded as far as possible. It was a rule of our law that intent and knowledge were not matters that could be proved or put in issue. “It is common learning,” said one of the judges of King Edward IV., “that the intent of a man will not be tried, for the devil himself knoweth not the intent of a man.”[[386]] The sole question which the courts would entertain was whether the defendant did the act complained of. Whether he did it ignorantly or with guilty knowledge was entirely immaterial. This rule, however, was restricted to civil liability. It was early recognised that criminal responsibility was too serious a thing to be imposed upon an innocent man simply for the sake of avoiding a difficult inquiry into his knowledge and intention. In the case of civil liability, on the other hand, the rule was general. The success with which it has maintained itself in modern law is due in part to its undeniable utility in obviating inconvenient or even impracticable inquiries, and in part to the influence of the conception of redress in minimising the importance of the formal condition of penal liability.