Confronted by a biography so large and heavy that it could easily serve as a doorstop, one’s first thought is to wonder whether its subject merits so lengthy a work. As Macaulay pointed out in his review of Edward Nares’s gigantic biography of Lord Burghley, “unhappily the life of man is now three score years and ten,” and therefore we must allocate our time for reading wisely, according to the importance of the subject in hand. Of course, importance is not a natural quality that can be measured with exactitude. What is important to me may be trivial to you, and vice versa. But most people would agree that the French Revolution was and remains an important event in human history, and therefore that its major figures, among them Jean-Paul Marat, are worthy of biographical study.

Keith Michael Baker, in this magisterial biography of Marat, obviously the fruit of decades of reading and research, has attempted as rounded a picture of his subject as possible, though the fact remains that Marat was not a very rounded character. It seems that he was born for extremism, monomania, and calling down anathema; he was incapable of long-lasting friendship, utterly lacking in charm and humor or any sense of irony, and given to paranoia and its reverse, the grossest self-adulation. Physiognomy is no doubt an inexact study, but one cannot help but feel that the portrait of him by Jean-François Garneray captured his ugliness rather well, an ugliness not only of body but of soul. That such a man, after his death, should have—for a time—been the object of mass adulation is testimony to the fevered disorder of the period.

Still, there is no doubt that Marat was a remarkable man. Someone possessed of his abilities and of better character might have been, in more propitious times, admirable. He was born in 1743 in the Prussian principality of Neuchâtel in Switzerland. His father was a Sardinian former Catholic priest, converted to Calvinism, and his mother was of French Huguenot descent. Given this mixed heritage, the son added the final t to his surname to make it look more French.

Marat struck out at an early age on his own, and by the age of twenty-one was living in England. Practicing medicine in a completely unregulated market, he managed to obtain a medical doctorate from the University of St Andrews in Scotland. He had a fashionable clientele and could easily have spent the rest of his life in great prosperity, catering to the needs, or at least the wishes, of the rich. This alone is remarkable.

But Marat was never much motivated by the prospect of wealth. Renown and glory, literary and scientific, were what he mainly sought. His first writings, philosophical, political, and medical, were in English. He observed English political life, which was both comparatively free and very corrupt. He conceived in England a contempt and hatred for representative democracy which he retained for the rest of his life, for he assumed that it must always be as deformed as it was in the England of his day.

He returned to France when his literary efforts in England, including his anonymous tract The Chains of Slavery, met with no success. Rather surprisingly, he established himself in Paris as a fashionable doctor, thanks, perhaps, to a chance cure of the Marquis de Châteauneuf, whose pulmonary complaints all the other doctors of the city had failed to alleviate. As a result, Marat was appointed doctor to the guardsmen of the Comte d’Artois, Louis XVI’s youngest brother and the future (highly reactionary) Charles X.

Once again, fashionable medical practice among the rich did not satisfy him, and this time he devoted himself to the study of physics, for many years and at great economic cost to himself. He believed himself to have made fundamental discoveries in the physics of flame, in optics, and in electricity, and he published books on those subjects, but unfortunately—or so he complained—was never recognized as a great scientist. This oversight he attributed, in the paranoid fashion that he was to exhibit for the rest of his life, to the envy, stupidity, and corruption of academicians such as Condorcet and Lavoisier. Although he detested scientific academies, he hoped for a time to become the director of one such in Madrid, being perfectly prepared to grovel to his social superiors in order to do so. The fact that even such groveling failed to advance him no doubt reinforced his social radicalism and bloodthirstiness.

The calling of the Estates General in 1789 and the subsequent revolution gave him his chance. From then on, he devoted himself exclusively to politics. He turned himself into L’Ami du peuple, the Friend of the People, which was also the name of the incendiary news sheet that he wrote and published, mainly in clandestinity. He was a consistent advocate of violence, believing that prosperity, happiness, and peace would be achieved only if the bad people—aristocrats, bankers, moderates—were eliminated. At first, he thought that it would be enough to kill five to six hundred, prophylactically, as it were. But the longer the enemies of the revolution were not killed, the more of them there were to kill, such that he came to think in hundreds of thousands rather than in mere hundreds. Charlotte Corday, about whom Baker says surprisingly little, killed Marat in the name of the moderation that he so excoriated and of which he was so contemptuous.

The felicific calculus method of thinking about murder is a permanent temptation in modern life. To take just one example from recent headlines, consider the reaction to the killing of UnitedHealthcare’s C.E.O. Brian Thompson by Luigi Mangione. In one French book, published last year, we are informed that “the killer of Brian Thompson stole several decades of life from him” but also that “Thompson had stolen thousands of lives for the sake of profit, and was even rewarded with millions of dollars” for having done so. If the author’s point were not already clear enough, the book’s title, Saint Luigi, makes it obvious. This sort of reasoning can easily give way to a belief that one murder might have saved thousands of lives, which is exactly what Marat argued.

For most people, Baker’s Marat will contain more detail about a deeply unattractive man than they will want to have, but the detail conduces to the consistency of the picture of Marat’s psychology. He was the kind of man in whom ambition is the outstanding characteristic, a thirst for glory that very early on in his career, in a book titled An Essay on the Human Soul, published in 1772 when he was twenty-nine, he identified as being more fundamental to human psychology than sympathy. He may have been the friend of “the people,” but not of people. He conceived of the people not as they were but as he felt they ought to have been. Time and again he expressed his disdain for them because they failed to act as he thought they ought to have acted. They were too cowardly, frivolous, stupid, and shortsighted to act in their own interest, at least as laid down by him. Most of all, they failed to kill those whom he thought they should have killed. He approved of them only when they rose up in violence and slaughtered those whom both they and he considered their enemies.

There is a problem of political philosophy, still unsolved (because insoluble), that runs quite explicitly through Baker’s account of Marat’s political life. Marat had conceived a contempt for representative democracy from having observed it close up in England. Everything about it was corrupt, from the choosing of the candidates to the franchise to the candidates themselves. Moreover, even if the sources of such corruption could be corrected, the system would still not be democratic, for there would be no way of ensuring that the government complied with the general will once it was elected. Marat wanted a more direct democracy, in which the people’s will might be expressed and given force all the time, constantly. He wanted government to be what Ernest Renan said a nation was, a plebiscite that took place every day. Only by such constant plebiscite could government comply with the wishes of the people.

There are obvious problems with both direct and representative democracy. It is impossible to gauge the wishes of a large population on every subject all the time. Most decisions have to be taken without popular assent. If such assent is sought, it can quickly degenerate into mob rule, and those who make the most noise are not necessarily—in fact, are usually not—those with the most widespread opinions.

On the other hand, representative democracy often degenerates into an elective dictatorship, albeit one limited by future election. There is no possibility, for example, of a legitimate government either in Britain or France, if by legitimacy is meant that the government fulfills the wishes of a majority of the population, or even of a very large part of it. The only source of legitimacy possible for a British or French government is its coming to power honestly and according to the rules laid down. The current British government, for example, obtained an overwhelming majority of seats in the legislature with the votes of about a third of the electorate, and the third-largest party had to obtain more than thirty times the number of votes to have a seat in the legislature as the winning party. Only someone with the soul of a bureaucrat, for whom adherence to procedure is the highest good, could call this democratic.

There is no entirely satisfactory way of resolving the tension between direct and representative democracy, at least in any large-scale polity. But as far as one can tell, Marat never lost his belief in a perfect solution, nor did he recognize anything like bloodlust in his desire to eliminate enemies.

He could on occasion be very clear-sighted, however. An instructive example is the situation in Saint-Domingue (Haiti) immediately after the revolution in France. The white planters of France’s most lucrative colony claimed independence for themselves while denying equality to free mulattoes and blacks. They thus set themselves up for future genocide under the Emperor Dessalines, precisely as Marat had foreseen.

Resentment runs like a red thread through Marat’s life. He seemed incapable of discussing anything, even questions of physics, without belittling, denigrating, or insulting those who either came before him or who disagreed with him in the present. Baker must have tried hard to sympathize with him, for he has lived with him for years, but in the end, it seems to have been almost impossible for him to do so because Marat was so deeply unattractive as a man. Baker quotes a great deal from Marat’s writing, much of which consists of piling up denunciation upon denunciation, such that one feels like washing oneself after reading it. Not only would one not have wanted to meet Marat; indeed, one would have wanted not to meet him.

I doubt that any biography in English of Marat will be called for after this book, although perhaps an abridged version might be. It is well written, though I have one or two tiny quibbles, for example the continual, and to me irritating, use of “let’s” rather than “let us” in translations of highly rhetorical political speeches, and the translation of la liberté ou la mort as “live free or die,” when “liberty or death” would be more natural.

I have a slight criticism of the publisher too. The book is more than nine hundred pages long, its print is small, its margins narrow, and its weight more than three pounds. This makes it unpleasant, physically, to read, and will perhaps entomb it as a monument of scholarship rather than spread it as a book to be read—as it deserves. It would have done the book and its author a service, then, if it had been published in more than one volume, as, indeed, was Nares’s biography of Lord Burghley.