All ethical theories accord some importance to human happiness. They differ first in their conception of what that happiness consists in, secondly in views of how an agent's own personal happiness is aligned with, or traded against, the general happiness, and thirdly in whether it is necessary to acknowledge any other end for human action. The simplest doctrine is that happiness is itself quite straightforward, consisting for example in occasions of pleasure; that agents only do seek or ought to seek their own happiness; and that there is no other possible or desirable end of action (see hedonism). The Cyrenaics may have held a doctrine along these lines. Complexity arises with more subtle conceptions of the nature of happiness (see, for example, stoicism, epicureanism, felicific calculus), and more concern for the possibility of incorporating the good of others into one's own ends (see, for example, altruism, friendship, prisoners' dilemma). Finally, theories of ethics that are not consequentialist in nature may recognize other ethically important features of action than those arising from the goal of maximizing either personal or social happiness. For the paradox of happiness, see hedonism, paradox of.