Children have strong motor impulses, which are at first little controlled. Inhibition is a late development and is largely a result of education.
If the motor impulses remain strong, or become stronger in the presence of development with exercise, while inhibition remains weak, we have a criminal.
Inhibition is the function performed by the highest and last-formed brain-cells. These brain cells may be undeveloped either from want of exercise, that is, education, or from hereditary weakness, or, having been developed may have undergone degeneration, under the influence of alcohol, or from hereditary or acquired disease.
Motor impulses, as the springs of action, are common to all animals. In the lower animals inhibition is external, and never internal or subjective. In man it may be internal or external.
It is internal or subjective in those whose higher brain centres are well developed and normal. Their auto-inhibition is such that all their motor impulses are controlled and directed in the best interests of society.
It is external only in those whose higher brain centres are either undeveloped or diseased. These constitute the criminal classes. Their motor impulses are unrestrained. They offer a low or reduced resistance to temptation.
Weak or absent resistance in the face of a normal motor impulse whose expression injuriously affects another, is crime, and a criminal is one whose power of resistance to motor impulses has been reduced by disease, hereditary or acquired, or is absent through arrested development.
A confirmed criminal is one in whom the frequent recurrence of an unrestrained impulse injurious to others has induced habit.
Auto-inhibition is defective or absent, and society must in her own interest provide external restraint, and this we call law.
Criminals are, therefore, mental defectives, and may be defined for sociological purposes as those in whom legal punishment for the second time, for the same offence, has failed to act as a deterrent.
M. Boies, in "Prisoners and Paupers," says that conviction for the third time for an offence, is proof of hereditary criminal taint.
The existence of motor impulses in the human animal is normal. They vary in strength and force. We cannot eradicate, we can only control them.