It is the activity of the intellect that constitutes complete human happiness - provided it be granted a complete span of life, for nothing that belongs to happiness can be incomplete.
Each thing tends to move towards its own nature. I always desire happiness which is my true nature. My nature is never a burden to me. Happiness is never a burden to me, whilst sorrow is.
It is in everybody's interest to seek those [actions] that lead to happiness and avoid those which lead to suffering. And because our interests are inextricably linked, we are compelled to accept ethics as the indispensable interface between my desire to be happy and yours.
Strange is our situation here on Earth. Each of us comes for a short visit, not knowing why, yet sometimes seeming to divine a purpose. From the standpoint of daily life, however, there is one thing we do know: that man is here for the sake of other men - above all for those upon whose smiles and well-being our own happiness depends.
The third-rate mind is only happy when it is thinking with the majority. The second-rate mind is only happy when it is thinking with the minority. The first-rate mind is only happy when it is thinking.