een recognized at all times, wherever criminal law has been
administered, with even the slightest reference to the principles of
common morality and justice.

I quote again on this subject from Mr. Bishop: "The doctrine of _the
intent_ as it prevails in the criminal law, is necessarily _one of the
foundation principles of public justice_. There is only one criterion by
which the guilt of man is to be tested. It is whether the mind is
criminal. Criminal law relates only to crime. And neither in
philosophical speculation, nor in religious or moral sentiment, would
any people in any age allow that a man should be deemed guilty unless
his mind was so. It is, therefore, a principle of our legal system, as
probably it is of every other, that _the essence of an offence is the
wrongful intent without which it cannot exist_." (_1 Bishop's Crim. Law,
Sec.287._)

Again, the same author, writing on the subject of _knowledge_, as
necessary to establish the intent, says: "It is absolutely necessary to
constitute guilt, as in indictments for uttering forged tokens, or other
attempts to defraud, or for receiving stolen goods, and offences of a
similar description." (_1 Crim. Prac. Sec.504._)

In regard to the offence of obtaining property by false pretenses, the
author says: "The indictment must allege that the defendant knew the
pretenses to be false. _This is necessary upon the general principles of
the law_, in order to show an offence, even though the statute does not
contain the word 'knowingly.'" (_2 Id. Sec.172._)

As to a _presumed knowledge_ of the law, where the fact involves a
question of law, the same author says: "The general doctrine laid down
in the foregoing sections," (i.e. that every man is presumed to know the
law, and that ignorance of the law does not excuse,) "is plain in itself
and plain in its application. Still there are cases, the precise nature
and extent of which are not so obvious, wherein ignorance of the law
constitutes, in a sort of indirect way, not in itself a defence, but a
foundation on which another defence rests. Thus, if the guilt or
innocence of a prisoner, depends on the fact to be found by the jury, of
his having been or not, when he did the act, in some precise mental
condition, _which mental condition is the gist of the offence_, the jury
in determining this question of mental condition, _may_ take into
consideration his ignorance or misinformation in a matter of law. For
example, to cons