"When pleasure is asserted to be the end of living, we are not then to understand that violent kind of delight or joy which arises from the gratification of the senses and passions, but merely that placid state of mind, which results from the absence of every cause of pain or uneasiness. Those pleasures, which arise from agitation, are not to be pursued as in themselves the end of living, but as means of arriving at that stable tranquility, in which true happiness consists."