Hume wrote about fundamental similarities and dissimilarities between human and nonhuman animals. His work was centered on the cognitive and emotional lives of animals, rather than their moral or legal standing, but his theories have implications for issues of moral standing. The historical background of these controversies reaches to ancient philosophy and to several prominent figures in early modern philosophy. Hume develops several of the themes in this literature. His underlying method is analogical argument and his conclusions are generally favorable regarding the abilities in animals. Hume does not attribute a moral sense or capacity of judgment to animals, but he does suggest that their actions exhibit moral qualities, such as other-regarding instincts. Hume allows in-kind differences in both demonstrative reason and moral judgment, but in the domains of both causal reason and moral agency he believes there are differences of degree rather than of kind. Hume's most significant philosophical contribution was to move as far as anyone before him to a naturalistic explanation of human and nonhuman minds that invited psychological and epistemological examination of minds by using the identical methods and categories for man and beast.