That there was no law of nature that man should love mankind, and that, if there had been any love on earth hitherto, it was not owing to a natural law, but simply because men have believed in immortality.
 Fyodor Dostoyevsky, The Brothers Karamazov (1880). copy citation

Context

““ I will tell you instead, gentlemen, another interesting and rather characteristic anecdote of Ivan Fyodorovitch himself. Only five days ago, in a gathering here, principally of ladies, he solemnly declared in argument that there was nothing in the whole world to make men love their neighbors. That there was no law of nature that man should love mankind, and that, if there had been any love on earth hitherto, it was not owing to a natural law, but simply because men have believed in immortality. Ivan Fyodorovitch [pg 071] added in parenthesis that the whole natural law lies in that faith, and that if you were to destroy in mankind the belief in immortality, not only love but every living force maintaining the life of the world would at once be dried up.” source