We shall see later that the mens rea or guilty mind includes two, and only two, distinct mental attitudes of the doer towards the deed. These are intention and negligence. Generally speaking, a man is penally responsible only for those wrongful acts which he does either wilfully or negligently. Then and only then is the actus accompanied by the mens rea. Then and then only do the two conditions of liability, the material and the formal, coexist. In this case only is punishment justifiable, for it is in this case alone that it can be effective. Inevitable accident or mistake—the absence both of wrongful intention and of culpable negligence—is in general a sufficient ground of exemption from penal responsibility. Impunitus est, said the Romans, qui sine culpa et dolo malo casu quodam damnum committit.[[326]]
We shall consider separately these two conditions of liability, analysing first the conception of an act, and secondly that of mens rea in its two forms of intention and negligence.[[327]]
§ 128. Acts.
The term act is one of ambiguous import, being used in various senses of different degrees of generality. When it is said, however, that an act is one of the essential conditions of liability, we use the term in the widest sense of which it is capable. We mean by it any event which is subject to the control of the human will. Such a definition is, indeed, not ultimate, but it is sufficient for the purpose of the law. As to the nature of the will and of the control exercised by it, it is not for lawyers to dispute, this being a problem of psychology or physiology, not of jurisprudence.
(1) Positive and Negative Acts. Of acts as so defined there are various species. In the first place, they are either positive or negative, either acts of commission or acts of omission. A wrongdoer either does that which he ought not to do, or leaves undone that which he ought to do. The term act is often used in a narrow sense to include merely positive acts, and is then opposed to omissions or forbearances instead of including them. This restriction, however, is inconvenient. Adopting the generic sense, we can easily distinguish the two species as positive and negative; but if we restrict the term to acts of commission, we leave ourselves without a name for the genus, and are compelled to resort to an enumeration of the species.
(2) Internal and external acts. In the second place, acts are either internal or external. The former are acts of the mind, while the latter are acts of the body. In each case the act may be either positive or negative, lying either in bodily activity or passivity, or in mental activity or passivity. To think is an internal act; to speak is an external act. To work out an arithmetical problem in one’s head is an act of the mind; to work it out on paper is an act of the body. Every external act involves an internal act which is related to it; but the converse is not true, for there are many acts of the mind which never realise themselves in acts of the body. The term act is very commonly restricted to external acts, but this is inconvenient for the reason already given in respect of the distinction between positive and negative acts.
(3) Intentional and unintentional acts. Acts are further distinguishable as being either intentional or unintentional. The nature of intention is a matter to which particular attention will be devoted later, and it is sufficient to say here that an act is intended or intentional when it is the outcome of a determination of the actor’s will directed to that end. In other words, it is intentional when it was foreseen and desired by the doer, and this foresight and desire realised themselves in the act through the operation of the will. It is unintentional, on the other hand, when, and in so far as, it is not the result of any determination of the will towards a desired issue.
In both cases the act may be either internal or external, positive or negative. The term omission, while often used in a wide sense to include all negative acts, is also used in a narrower signification to include merely unintentional negative acts. It is then opposed to a forbearance, which is an intentional negative act. If I fail to keep an appointment through forgetfulness, my act is unintentional and negative; that is to say, an omission. But if I remember the appointment, and resolve not to keep it, my act is intentional and negative; that is to say, a forbearance.
The term act is very commonly restricted to intentional acts, but this restriction is inadmissible in law. Intention is not a necessary condition of legal liability, and therefore cannot be an essential element in those acts which produce such liability. An act is an event subject to the control of the will; but it is not essential that this control should be actually exercised; there need be no actual determination of the will, for it is enough that such control or determination is possible. If the control of the will is actually exercised, the act is intentional; if the will is dormant, the act is unintentional; but in each case, by virtue of the existence of the power of control, the event is equally an act. The movements of a man’s limbs are acts; those of his heart are not. Not to move his arms is an act; not to move his ears is not. To meditate is an act; to dream is not. It is the power possessed by me of determining the issue otherwise which makes any event my act, and is the ground of my responsibility for it.
Every act is made up of three distinct factors or constituent parts. These are (1) its origin in some mental or bodily activity or passivity of the doer, (2) its circumstances, and (3) its consequences. Let us suppose that in practising with a rifle I shoot some person by accident. The material elements of my act are the following: its origin or primary stage, namely a series of muscular contractions, by which the rifle is raised and the trigger pulled; secondly, the circumstances, the chief of which are the facts that the rifle is loaded and in working order, and that the person killed is in the line of fire; thirdly, the consequences, the chief of which are the fall of the trigger, the explosion of the powder, the discharge of the bullet, its passage through the body of the man killed, and his death. A similar analysis will apply to all acts for which a man is legally responsible. Whatever act the law prohibits as being wrongful is so prohibited in respect of its origin, its circumstances, and its consequences. For unless it has its origin in some mental or physical activity or passivity of the defendant, it is not his act at all; and apart from its circumstances and results it cannot be wrongful. All acts are, in respect of their origin, indifferent. No bodily motion is in itself illegal. To crook one’s finger may be a crime, if the finger is in contact with the trigger of a loaded pistol; but in itself it is not a matter which the law is in any way concerned to take notice of.