In death, Marat became an icon to the Montagnards faction of the Jacobins as well as the greater sans-culotte population, and a revolutionary martyr; according to contemporary accounts, some even mourned him with a kind of prayer: "O heart of Jesus!

[10] His father studied in Spain and Sardinia before becoming a Mercedarian friar in 1720, at age 16, but at some point left the order and converted to Calvinism, and in 1740 immigrated to the Protestant Republic of Geneva.

His mother, who had Huguenot background from both sides of her family, was the daughter of French perruquier Louis Cabrol, originally from Castres, Languedoc, and Genevan citizen after 1723, and his wife Pauline-Catherine Molinier.

His first political work, Chains of Slavery (1774), inspired by the extra-parliamentary activities of the disenfranchised MP and later Mayor of London John Wilkes, was most probably compiled[citation needed] in the central library there.

In Paris, his growing reputation as a highly effective doctor along with the patronage of the Marquis de l'Aubespine (the husband of one of his patients) secured his appointment as physician to the bodyguard of the Comte d'Artois, Louis XVI's youngest brother.

The first of Marat's large-scale publications detailing his experiments and drawing conclusions from them was Recherches Physiques sur le Feu (English: Research into the Physics of Fire), which was published in 1780 with the approval of the official censors.

Apart from his major works, during this period Marat published shorter essays on the medical use of electricity (Mémoire sur l'électricité médicale (1783)) and on optics (Notions élémentaires d'optique (1784)).

[28] Marat's entry contained many radical ideas, including the argument that society should provide fundamental natural needs, such as food and shelter, if it expected all its citizens to follow its civil laws, that the king was no more than the "first magistrate" of his people, that there should be a common death penalty regardless of class, and that each town should have a dedicated "avocat des pauvres" and set up independent criminal tribunals with twelve-man juries to ensure a fair trial.

[30] Marat anonymously published his first contribution to the revolution in February 1789, titled Offrande à la Patrie (Offering to the Nation), which touched on some of the same points as the Abbé Sieyès' famous "Qu'est-ce que le Tiers État?"

On 14 July, three days after Louis XVI dismissed Jacques Necker as his financial advisor, enraged Parisians attacked the Hotel des Invalides and the Bastille, marking the first insurrection of the French Revolution.

Marat was not directly involved in the Fall of the Bastille but sought to glorify his role that day by claiming that he had intercepted a group of German soldiers on Pont Neuf.

On 12 September 1789, Marat began his own newspaper, entitled Publiciste parisien, before changing its name four days later to L'Ami du peuple ("The People's friend").

[35] In January 1790, he moved to the radical Cordeliers section, then under the leadership of the lawyer Danton,[30] was nearly arrested for his attacks against Jacques Necker, Louis XVI's popular Finance Minister, and was forced to flee to London.

[37] This led him to call for police intervention, which resulted in the suppression of the fraudulent issues, leaving Marat the continuing sole author of L'Ami du peuple.

Ernest Belfort Bax disputed this claim, saying that on appearing once again in the upper daylight of Paris, Marat was almost immediately invited to assist the new governing body with his advice, and had a special tribune assigned to him.

Montmarin was notoriously and openly a courtier, who wished to see the allies in Paris, and his royal master reinstated, and who was proved, beyond the shadow of a doubt, to have been actively engaged in plotting to this end; yet, on being brought to trial, he was acquitted, and, as if to lend emphasis to the acquittal, the judge himself, descending from the bench, gave him his arm as he walked out of court.

[44] Those arrangements would include a collection of mercenaries grouped as "Marsellais" though they were "foreign vagabonds, dregs of all nations, Genosee, Corsicans and Greeks led by a Pole named Lazowski.

[47] On 3 September, the second day of the massacres, the Committee of Surveillance of the Commune published a circular that called on provincial Patriots to defend Paris and asked that, before leaving their homes, they eliminate counter-revolutionaries.

679 of L'Ami du Peuple we have the following advice: Guard the King from view, put a price on the heads of the fugitive Capets, arm all the citizens, form a camp near Paris, press forward the sale of the goods of the ‘emigrants,’ and recompense the unfortunates who have taken part in the conquest of the Tuileries, invite the troops of the line to name their officers, guard the provisions, do not miss a word of this last advice, press the judgment of the traitors imprisoned in the Abbaye; ... if the sword of justice do at last but strike conspirators and prevaricators, we shall no longer hear popular executions spoken of, cruel resource which the law of necessity can alone commend to a people reduced to despair, but which the voluntary sleep of the laws always justifies.

Finally people gathered from all sides... Oh my dear friend, we are all in a state of dreadful consternation.There is an exculpatory article in No.12 of Marat's Journal de la République, occasioned by the virulent attacks of the Girondins in the Convention on the Commune, the Committee of Supervision, and above all on Marat himself, with reference to the massacres:The disastrous events of the 2nd and 3rd of September, which perfidious and venal persons attribute to the Municipality, has been solely promoted by the denial of justice on the part of the Criminal tribunal which whitewashed the conspirator Montmarin, by the protection thus proclaimed to all others conspirators, and by the indignation of the people, fearing to find itself the slave of all the traitors who have for so long abused its misfortunes and its disasters.

This perspective of affairs is summed up in the passages of Mr. Bowen-Graves quoted by Ernest Belfort Bax:Marat's part in these last terrible events has been constantly and grossly misrepresented.

The Swiss guards, the rank and file have fallen, sacrificed to their fidelity to a master who had deserted and forgotten them; but officers, courtiers, chevaliers de poignard, are lively as ever, intriguing, plotting, vapouring in street and café, openly rejoicing in the triumph which German armies will give them measuring, compasses in hand, the distance between Verdun and Paris.

Then, while the tocsin was clanging, and the alarm cannon roaring, and the Girondin minister could find nothing better to suggest, with his unseasonable classicism, than carrying into the South the statue of liberty, Paris answered with one instinct to Danton's thundering defiance, and perpetrated that tremendous act of self-defence at which we shudder to this day.

The reaction hid its head and cowered; and within the month the ragged volunteers of the Republic were hurling back from the passes of the Argonne the finest soldiery which Europe could produce.

[48]On 2 September, news arrived in Paris that the army of the Duke of Braunschweig had invaded France and the fortress of Verdun had quickly fallen, and that the Prussians were rapidly advancing towards the capital.

The news that Verdun had been taken... provoked their resentment and vengeance.’[50] It was enough for the Legislative Assembly, at the vigorous request of the Commune, to issue a statement to the French people on 4 September in which it promised "that it would fight with all its powers against the king and the royal government" so that the slaughter would end the same day and Parisians would go to the front.

Marat was in his bathtub on 13 July when a young woman from Caen, Charlotte Corday, appeared at his flat, claiming to have vital information on the activities of the escaped Girondins who had fled to Normandy.

[citation needed] At that moment, Corday rose from her chair, drawing out from her corset a five-inch (13 cm) kitchen knife, which she had bought earlier that day, and brought it down into Marat's chest, where it pierced just under his right clavicle, opening the brachiocephalic artery, close to the heart.

[59] Marat's assassination contributed to the mounting suspicion which fed the Terror during which thousands of the Jacobins' adversaries – both royalists and Girondins – were executed on charges of treason.

His heart was embalmed separately and placed in an urn in an altar erected to his memory at the Cordeliers to inspire speeches that were similar in style to Marat's journalism.