The Meaning of Life
Aristotle writes extensively about happiness in his book the Nicomachean Ethics. In it he says "what is always chosen as an end in itself and never as a means to something else is called final in an unqualified sense. This description seems to apply to happiness above all else: for we always choose happiness as an end in itself and never for the sake of something else." The rest of the work considers the best means to achieve this ultimate end and Aristotle ultimately concludes that a life lived according to the virtues is the best means to this ultimate end. Given this analysis the question becomes how does joy differ from this?
In his book Ten Philosophical Mistakes, Mortimer Adler points out that a common mistake, even among professional philosophers, is to believe that happiness is a psychological state as opposed to an ethical state. Perhaps this is the best way to distinguish joy from happiness. To say that joy is a psychological state is to say that it can be understood in a given moment in time and is fleeting or transient. Joy is not a condition we can sustain for any extended period of time. We feel joy in the face of certain events in our lives but then return to a prior state. It may not even be possible to intend to experience joy. Could one artificially manufacture a scenario with the express intent of deriving joy from it? However, if Aristotle's analysis is correct, one can intend to live a happy life by acting in accordance with the virtues. To do this he counsels that we practice to get into the habit of acting virtuously. Clearly, there is an intent here which seems to be a crucial difference.
Additionally, while joy can be experienced and evaluated in specific given moments in time, Aristotle advises that we look upon happiness as a quality of our entire life. A life well lived is a happy life but this must be viewed as a whole. Indeed, "one swallow does not make a spring, nor does one sunny day; similarly, one day or a short time does not make a man blessed and happy." We localize joy but must generalize happiness.
Though separated by centuries and culture the Dalai Lama concurs in large part with this Aristotelian interpretation of happiness. In his book The Art of Happiness, he shows how one can train the mind to be happy. Again, this illustrates the role of intent in the process of achieving happiness. He also points out that to the extent that we are happy our attitude plays a large role. The reverse holds true as well. To the extent that we are unhappy we have only our attitude to blame.
In this respect, the Dalai Lama's message is also similar to the ancient Stoic idea of happiness. As the Stoic philosopher and Roman Emperor Marcus Aurelius pointed out "the happiness of your life depends upon the quality of your thoughts." While achieving happiness is not as easy as simply deciding to be happy a proper attitude is essential. And, the recognition that external things do not control our happiness. As Seneca once said: "He that is not content in poverty, would not be so neither in plenty; for the fault is not the thing, but in the mind."
This brings me to one last contrast. It is often correctly said that money cannot buy happiness. But, it might be possible for money to buy joy or at least be able to create conditions where the experience of joy is likely. Many people feel joy when buying a new car, buying clothes, or whatever. But, this feeling subsides once the newness of the item wears off. Those who do not recognize the difference between this psychological state of joy and the ethical state of happiness return to purchase new things in the hopes that these will bring happiness. But, since happiness is a quality of one's life as opposed to a fleeting psychological state, this strategy is doomed to fail.
It seems that more and more things are required to keep the feeling of joy alive. But, it was Epicurus who recognized that there are only three things required for happiness: friendship, freedom, and contemplation. Of these, one is most important for Epicurus: “Of all the means which are procured by wisdom to ensure happiness throughout the whole of life, by far the most important is the acquisition of friends.”