If now we look back at the law of Malthus we shall realise the enormous significance of the law of Spencer. In this respect we have the advantage over Malthus that we are aware, as he was not, of the great fact of organic evolution. We discover, then, that an actual consequence of the pressure of population, leading as it does to the struggle for existence, and, in the main, the survival of higher types, is that the rate of fertility falls. This conception of the fall in the birth-rate--which, it is maintained, has been a great factor in all organic progress--was entirely absent from the mind of Malthus. In a word, the unlimited multiplication which Malthus observed leads to its own correction. It provides abundance of material for natural selection to work upon, and then the survival-value of individuation, wherever it appears, asserts itself, with the consequence that the rate of multiplication declines. This is actually to be observed to-day. Malthus desired that we should postpone marriage to later ages so as to lower the birth-rate. The increasing necessity and demand for individuation is effecting that which Malthus desired. The average age at marriage has been rising in our own country in both sexes during the last thirty years: and the evidence shows that as civilisation advances the age of marriage becomes later and later. Professor Metchnikoff has discussed some aspects of this question in his book _The Nature of Man_. =The intensive culture of life.=--For every student of progress, and not least for the eugenist, Spencer's law is a warrant of hope and a promise of better things to come. It teaches that in the development of higher--that is to say, more specialised--that is to say, more individualised--organic types, Nature is working already, and has been working for ages, towards the elimination of the brutal elements in the struggle for existence. This is, of course, what every worker for progress, and every eugenist in especial, desires. Spencer's discovery teaches also that individuality compensates a species for loss of high fertility. The survival-value of individuation is greater than the survival-value of rapid multiplication. _The very fact of progress is the replacement of lower by higher life, the supersession of the quantitative by the qualitative criterion of survival-value, the increasing dominance of mind over matter, the substitution of the intensive for the merely extensive cultivation of life._ These various phrases express, I believe, various aspects of one and the same great fact, and I only wish it were possible to include here an exhaustive study of the conception which may be expressed by the phrase “the intensity of life”--as distinguished from its mere extension. There is, I believe, a real and significant analogy between the introduction of what is called intensive cultivation in agriculture, and the eugenic principle which seeks to replace the extensive by the intensive cultivation of human life.