Psychologists and self-help gurus link happiness to positive emotions and feelings. To be happy, you need to go about maximizing your positive responses to life. It is true that happiness involves positive emotions and feelings. But the relentless pursuit of happy experiences can easily lead to unhappiness, which suggests that positive feelings are not the original cause of happiness itself. A better way of thinking about happiness is to see happiness as the product of the flourishing life.

Mark Vernon, author of Wellbeing, argues that happiness is, or ought to be, a by-product of a life lived well. This view has an impressive pedigree, running all the way back to ancient times. It is first articulated in Aristotle and the Stoics.

The Stoics have a fascinating account of how happiness binds us to the natural world. Like other ancient philosophers, the Stoics see the point of philosophy as being to achieve a state of happiness or flourishing (eudaimonia). But the way that the Stoics understood happiness or flourishing is quite different to how we`d understand it today.

Eudaimonia literally means: `the happiness of the spirit within`. What is this spirit (daimon) within? And how did the Stoics understand its happiness?

The Stoic spirit is the rational part of the human soul. The Stoics were intensely rational in their approach to life. A calm, rational outlook, the Stoics believed, is the natural human disposition. Passion and inner turmoil are unnatural experiences ephemera caused by our confusion about the facts of life. Rational tranquility, while natural, is not easily achieved. To enjoy the equanimity that is the gift of human nature, we need to get our thinking straight. We need to establish an inner vigilance, a spiritual police and tribunal, focused on using reason to combat the passions. By looking at the passions in the light of reason, the Stoics argued, it is possible to liberate oneself from the dominance of unruly passions. This is what the Stoics sought to achieve: to pare themselves back to their rational core so as to enjoy the happiness and tranquility of the spirit within.

The second point to note about Stoic eudaimonia has to do with the intimate relationship between the human spirit and the divine world-spirit, God. This is not the God of the Christian faith: the omnipotent ruler who watches us from a parallel world and adjudicates the affairs of humankind. The Stoic God exists in nature and, insofar as we are part of nature, in all of us. God is the rational spirit, or Logos, that inheres in nature and guides its law-like processes. There is a hidden law within the processes of life, and this law, the Stoics argue, is divine. When Seneca muses on the presence of God in a quiet forest grove, he is thinking of the set of ordered processes that have brought the grove into being. Similarly, when Marcus Aurelius advocates `living in accordance with nature`, he is expressing a religious intuition.

Here is a point worth thinking about. If reason is the expression of a divine power in nature, and we achieve eudaimonia through the use of reason, then Stoic happiness is more than just a feeling. Happiness is the pleasure of the Godhead within. Happiness is a pagan apotheosis.