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.
They may become less assertive under the constant control of a highly cultivated inhibition, but it is only in this way that they can be affected at all.