Here's a truly arresting thought - at least for those who think about ancient philosophy and philosophers - that I've never once heard voiced before. It comes from Darian Leader's excellent The New Black: Mourning, Melancholia and Depression.

This idea of absence is voiced not only in classical drama but also in philosophy. Thousands of books and articles have been devoted to Aristotle's logic, yet the basic, emotional problems he may have been grappling with seem to have gone completely unnoticed. The famous example of a syllogism, 'All men are mortal - Socrates is a man - Therefore Socrates is mortal', is not simply an abstract logical proposition but a statement about a real, live human being with whom Aristotle had a powerful relationship, even if the two had never met. If today a philosopher wrote a whole book in which the central example concerned the death of his intellectual master, we would surely pick up the emotional subtext. And that this question of morality is at the heart of Aristotle's concerns becomes even clearer if we remember his much-debated claim 'If a thing may be, it may also not be.' Isn't this, in fact, already a formulation of anticipatory grief?

Surprisingly, Leader overlooks the fact that Plato did indeed write whole books on the death of his intellectual master - or rather three of them, revisiting the death in dramatically different ways. And Socrates' death is present in many of the other dialogues too, off the page. If ever there was support needed for the startling impact that Socrates had upon the people he met, Leader's psychoanalytic suggestion would be, I think, a new line of enquiry.

The idea of repetition would seem to be the key to understanding what Plato was trying to work out: the difference of his portraits of Socrates suggest that he couldn't get to grips with the significance of this human being, or rather of his encounter with this human being. Similarly, that Socrates featured in all the dialogues suggests his work of mourning Socrates was never completed - all that is except the Laws. This is generally taken to be Plato's last work: perhaps the mourning was completed then; perhaps we can be glad it happened so late in Plato's life since it is also often regarded as an inferior piece of work.

Lacan would talk about the object a, the need to fill the lack created by the space Socrates vacated. Of course, Lacan's idea of love - giving what you don't have to someone to whom you can't give it - draws on the Symposium. Here love is described as a lack, and the analysis of love is put in the mouth of Diotima, not Socrates, since Socrates himself is driven by love, and so whilst knowing about love, in the sense of being acquainted with it, he doesn't understand this 'daimon'.

Incidentally, this is just one paragraph from Leader's book that otherwise looks at the difference between mourning and melancholia as first articulated by Freud, and variously discussed by his followers. It is also a manifesto against the biochemical approach to depression, that treats it mechanistically, like an infection or a period of sub-optimal functioning to be corrected like retuning a car. Rather, depression derives from the complex stories of people's lives and we are storing up great troubles for ourselves if we approach it by essentially papering over the cracks with pills or techniques like CBT.

For Leader, the nub of the problem is mourning, and the work of mourning, that follows all losses in life, be that from death, the end of relationships, or life's disillusionments. He suggests that the reason depression is on the rise, apart from the dark promotion of the 'condition' by the drug companies, is because as a society we are becoming so bad at mourning. It doesn't fit with our image of what it is to be human being - autonomous, transparent to science, productive to the economy, and the like. Rising levels of depression should not be responded to by yet more pills but by listening to that depression: it's perhaps a kind of protest against the conditions - emotional and spiritual, not material - people are being forced to live in.