Complex sentence: Spencer is sometimes credited for the Social Darwinist model that applied the law of the survival of the fittest to society; humanitarian impulses had to be resisted as nothing should be allowed to interfere with nature's laws, including the social struggle for existence.
Split into simpler sentences: Spencer is sometimes credited for the Social Darwinist model that applied the law of the survival of the fittest to society. Humanitarian impulses had to be resisted as nothing should be allowed to interfere with nature's laws, including the social struggle for existence.