Nature, I confess, has put into man a desire of happiness and an aversion to misery
 John Locke, An Essay Concerning Human Understanding (1689). copy citation

Context

“Practical principles, derived from nature, are there for operation, and must produce conformity of action, not barely speculative assent to their truth, or else they are in vain distinguished from speculative maxims. Nature, I confess, has put into man a desire of happiness and an aversion to misery: these indeed are innate practical principles which (as practical principles ought) DO continue constantly to operate and influence all our actions without ceasing: these may be observed in all persons and all ages, steady and universal;” source