Now all these propagate their kind.

The checks to the increase of this class, are the checks which are common to the lower animals, and which were elaborated in his first essay by Malthus.
They are vice and misery.
If it were not for moral restraint (not the limited restraint of Malthus, delayed marriages simply), but restraint in the wider sense, within as well as without the marriage bond, and including all artificial checks to conception, these two checks, vice and misery, would absolutely control the population of the world.
The mind of man has added to the checks which control increase in the lower animals, a new check, which applies to, and can be exercised only by himself, and the problem is, how far will misery and vice as checks to the population be eliminated, and moral restraint take their places?
And if this restraint must control and determine the population of the future how far will its exercise affect the moral and mental evolution of the race?
If moral restraint with the consequent limitations of families is the peculiar characteristic of the best people in the state, and the absence of this characteristic expressing itself in normal fertility is peculiar to the worst people of the state, the future of the race may be divined, by reference to the history of the great nations of antiquity.
An accumulating amount of evidence shows that society is face to face with this grave aspect of the population question.

The birth-rate of the unfit is steadily maintained.

Improved conditions of life increase the number that arrive at maturity and enter the procreative period, so that not only are defectives born into the world at a constant rate, but sanitary laws and a growing impatience with the sufferings of the poor, tend so to improve their conditions of life, as to increase their birth-rate and their chances of arriving at adult life.
Shortly stated then, the problem that society has to solve is this,--The birth-rate is rapidly declining amongst the most fit to produce the best offspring, while it is steadily maintained amongst the least fit, so that the relative proportion of the unfit born into the world is annually increasing.
What should be the State's attitude to this problem, and how it should attempt to solve it will be discussed in detail in a subsequent chapter.
Let it suffice to say now, that the right of the State to interfere directly with the limitation of families amongst the best classes would find few advocates amongst reformers.
The right of the State to say, however, that the criminal, the drunkard, the diseased, and the pauper, shall not propagate their kind should be stoutly maintained by all rational men.
Most of the nations of history have recognized the gravity of the population question, but they were mostly concerned with the tendency of the numbers in the State to increase beyond the means of subsistence, instead of the tendency to degeneration as it now concerns us..