What is Darwin’s point in chapter 3?
How well does it support his theory?
His point, which is key to his theory, is that there is a competition among life and that those with advantages will over time dominate others.
“Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection, in order to mark its relation to man’s power of selection.”
He basically extends the Malthusian doctrine and incorporates it into his theory of natural selection.
“It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage. Although some species may be now increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them.”
He acknowledges though that one cannot know the exact causes of what would cause a certain species to increase or decrease.
“What checks the natural tendency of each species to increase in number is most obscure.”
“We know not exactly what the checks are in even one single instance.”
“but probably in no one case could we precisely say why one species has been victorious over another in the great battle of life.”
He does end the chapter strangely though. I guess so that the reader will not be too saddened thinking about life having to struggle for existence.
“When we reflect on this struggle, we may console ourselves with the full belief, that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.”