Seagreen Robespierre.

We come across this use of words in Thomas Carlyle’s book “The French Revolution”; Part 2, Chapter 2 to be exact.

Carlyle's famous description of Robespierre; sometimes also written as, "the sea-green Incorruptible," at first sight might have been a portrayal of terror wearing his favourite sea-green coat.

"The Incorruptible" was the title given to him by his contemporaries. Most politicians would be proud to bear the name "Incorruptible" (though it would be tempting fate today); but adding the epithet "sea-green" has, as Carlyle intended, a slyly subversive effect: it evokes something from the depths, something reptilian.

And since Robespierre presided over the most bloodthirsty period of the French Revolution, the idea of him as The Incorruptible comes to suggest, not so much the decency of a politician who could not be bribed or deflected from his goals by self-interest, but other, quite different extremes: implacable, immovable, inflexible, inhuman.

It was not that he enjoyed killing; indeed, one of the mysteries of the man is knowing what he did enjoy. His private life was a pretty barren region.

As for the mass executions of the Terror (around 2,200 heads in Paris in the five months of Robespierre's ascendancy), it seems to have made him quite literally, sick: there were episodes of illness, especially in the last year of Robespierre's life, which can be read as a psychosomatic reaction to events, particularly the factional struggles at the height of the Terror, in 1794.

The only time he got close to the guillotine itself was when his own turn came to go under the Instrument, so in that respect he resembled Heinrich Himmler, who apparently also personally found mass murder distasteful.

The difference is that the ideals that drove Robespierre were fine and genuine: ideals of democracy, human rights and social justice.

Admittedly, they were couched in the language of his time, with much talk of virtue overcoming vice, of “le peuple, la nation & la patrie.” But there is no doubt about the essence of Robespierre's political programme or its sincerity.

For example, as when he proclaimed that he wanted; morality in place of egotism; honesty in place of an aristocratic concept of honour; behaviour governed by principle rather than convention, and the rule of reason rather than the tyranny of fashion.

Many politicians have said that they seek power, not for its own sake, but in order to achieve some great goal; Robespierre, as far as one can tell, actually meant it.

This doesn't exonerate him, any more than his own justification of the Terror:

"If the basis of popular government in peacetime is virtue, its basis in a time of revolution is both virtue and terror: virtue without which terror is disastrous, and terror, without which virtue is powerless. Terror is merely justice, prompt, severe and inflexible. It is therefore an emanation of virtue and results from the application of democracy to the most pressing needs of the country."

It sounds familiar.

When he talks of "enemies of the people", the analogies with Stalinist Russia, other 20th-century regimes, even the last President are so glaring that you have to keep reminding yourself that the French Revolutionaries were having to make everything up as they went along, against a very different background from that of the 20th-century tyrannies.

Apart from virtue and fear, religion was the force that Robespierre considered most essential to the progress of the humanity.

He was neither an atheist nor a freethinker: He attacked the atheism of some of his fellow revolutionaries with the same zeal that he directed against other deviations (because he also had a fundamental belief in the need for unanimity). The Cult of the Supreme Being, which he instituted, seems now like an easy compromise; a way of not have to choose between this God or that; but it is clear that Robespierre believed in his religion, as a rational response to humanity's need for a higher power.

He has always been a hero to some on the Left, despite the cold nature, the self-righteousness and the inevitable comparison with Danton - who said, mockingly, that real virtue was what he showed his wife every night.

We thus have a contrast between Danton's corruptible humanity and Robespierre's chilly idealism.