Hedonism
Many people believe that striving for happiness is a laudable aim.
When people are in dire straights they are advised to "put on a brave face" and try thier best to be happy.
This philosophy of hedonism has its roots, like many things, in Greek Philosophy, with it's earliest proponent being Democritus, who argued that joy was the ultimate aim in life, and that sorrow was to be avoided.
Acording to this theory we should at any particular moment just do whatever makes us happy, and avoid things which make us sad or sorrowful.
Utilitarianism
This idea was revived by Jeremy Bentham in the 18th Century, who argued that life could be divided into the basic emotions of pleasure and pain, and that whilst pain was to be avoided, pleasure was the sole good in life. He therefore argued for the "greatest good to the greatest number."
This philosophy, which became known as Utilitarianism, was expounded upon by John Stuart Mill who qualified the original philosophy by arguing that not all forms of happiness are morally neutral and that there are in fact "higher pleasures" and "lower pleasures." In the language of Mill:
"It is better to be a human dissatisfied than a pig satisfied; better to be Socrates dissatisfied than a fool satisfied"
In other words: It is not good enough to just be happy. Your happiness needs to be of a certain quality, or directed towards a higher end. According to Mill: It is not good enough to simply follow our inclinations from one moment to the next. Because whlst we may think that we know our own good. We can only possibly know in hindsight whether it was better for us to induce positive emotion with drugs (a lower pleasure) or with opera (ahigher pleasure), for instance.
Epicurius
Which brings us back to the many Greek responses to the idea of hedonism. Many Greeks belived that there were higher ends, which superceded our our immediate need for gratification and happiness.
This idea finds its most fruitful expression in the work of Epicurus, who argued that what matters is whether your life as a whole is a good one. He belived that what matters is eudomonia (a Greek word which can be loosely translated as "good spirit"), which refers to some inexplicable factor which reaches beyond transitory feelings and towards a more complete conception of what it means to live a good life, and can only be assessed over the entire course of a human life.
Many Greek theories preferred to look at life like this. These theories, rather than focussing on the consequences of our actions at any moment (in their production of pleasure and pain for instance), look at what it means to be human and what the end (telos) of our lives is, when taken as a whole.
According to these teleological theories, our lives should be measued according to whether, taken as a whole, they are good or virtuous.
Conclusion
And so... In answer to the question I proposed above: Is happiness desirable?
My answer is yes! It is! But what I mean by happiness is what Epicuriucs meant:
He lived a life in a commune, living with close friends and surviving on what nature provided, and he wanted his life to be judged by people in its totality - and whilst I'm not about to become a hippy. I can appreciate his philosophy much better than our modern conceptions of happiness: which lead to consumerism, casual sex and drunken debauchery.
When people look back at my life they will look at my life as a whole, because that is what human beings do. Whether I am happy or sad from one moment to the next is immatterial, as long as I continue with my goals in life, despite what fortune throws at me.
From my favourite poem:
"It matters not how strait the gate,
How charged with punishments the scroll,
I am the Captain of my fate,
I am the master of my soul."
- William Ernest Henley