Vices are those acts by which a man harms himself or his property.
Crimes are those acts by which one man harms the person or property of another.
Vices are simply the errors which a man makes in his search after his own happiness. Unlike crimes, they imply no malice toward others, and no interference with their persons or property.
In vices, the very essence of crime - that is, the design to injure the person or property of another - is wanting.
It is a maxim of the law that there can be no crime without a criminal intent; that is, without the intent to invade the person or property of another. But no one ever practises a vice with any such criminal intent. He practises his vice for his own happiness solely, and not from any malice toward others.
Unless this clear distinction between vices and crimes be made and recognized by the laws, there can be on earth no such thing as individual right, liberty, or property; no such things as the right of one man to the control of his own person and property, and the corresponding and coequal rights of another man to the control of his own person and property.
For a government to declare a vice to be a crime, and to punish it as such, is an attempt to falsify the very nature of things. It is as absurd as it would be to declare truth to be falsehood, or falsehood truth. - Lysander Spooner, Vices Are Not Crimes