way which meant that animals were not forced to consume each other to survive. David Hume made several observations about predation and suffering experienced by wild animals in Dialogues Concerning Natural Religion (1779), stating that the "stronger prey upon the weaker, and keep them in perpetual terror and anxiety". William Paley, in Natural Theology, described predation as being the most challenging of God's work to establish the utility of, nevertheless, he defended predation as the means to deal with the potentially catastrophic effects of animals producing more offspring than can possibly survive. The debate around predation and the problem of evil was significantly increased by the popularization of Charles Darwin's theory of natural selection. Some earlier Christians argued that violence in nature was a result of the fall of man, but evidence that predation has existed for millions of years before the evolution of humans and the concept of sin, indicates that while life has existed, there has never been a time where nature has been free from violence. Darwin himself questioned how the fact that the Ichneumonidae prey on the bodies of living caterpillars could be reconciled with the idea of an omnibenevolent God. Criticism of moral judgements Plutarch criticised the labelling of carnivorous animals such as lions, tigers and snakes as barbarous because for them killing is a necessity while for humans who can live off of "nature's beneficent fruits" killing is a "luxury and crime". The writer Edward Augustus Kendall discussed predation in his book of moral fables The Canary Bird (1799), in which he argued that predatory behavior by animals should not be judged by human moral standards and that "a prejudice against particular creatures, for fancied acts of cruelty is absurd". Philosophical pessimism Giacomo Leopardi, the Italian poet and philosopher, in Operette morali (1827) engaged in a dialogue with Nature in "Dialogue between Nature and an Icelander", which uses the inevitability of predation—such as a squirrel fleeing from a rattlesnake, only to run into the snake's open mouth—as a moral indictment on nature's cannibalism of its own offspring. The inevitability of such cycles of destruction and creation was a cause for Leopardi's philosophical pessimism. In Zibaldone, published posthumously in 1898, Leopardi argued that predation is the ultimate indication of the evil design of nature. Similar to Leopardi, the German philosopher Arthur Schopenhauer, in 1851, used the pain experienced by an animal being devoured by another