After finishing his law degree and becoming a lawyer, Muscat was lucky enough to encounter the good favours of one of the legal scribes (called uditore) of the Grand Master of the Knights Hospitaller, Manuel Pinto da Fonseca, who took him under his wing.
A long poetic work in Italian, called Sonnetto (Sonnet),[3] which he composed in 1758 was dedicated to Giammaria Azopardi Castelletti, Adriano Montana and Giuseppe Agius.
Another early writing, this time from 1771, when Muscat had thirty-six years of age, is called Replica delli Creditori (A Creditors’ Response).
Nevertheless, in his book Muscat touches upon a theme pertaining to political philosophy which he would go on to develop in other writings, namely the legal independence of a local government from outside interference (including the pope, his bishops or the Inquisition.
In general, he seems to have believed in the political system adhered to by the Hospitallers, albeit perhaps with a stronger dose of some egalitarian rights, and did not seem to harbour any thoughts of overturning their government.
Nevertheless, Muscat believed in the separation of Church and State, and in later years he succeeded in gaining the ear of the Hospitaller Grand Masters whom he served.
Muscat had no opportunity to put it into practice until around 1775, when newly-elected Grand Master Emmanuel de Rohan-Polduc appointed him as his avvocato del principato (which more or less corresponds to the office of an Attorney General).
The potential menace did not escape the local inquisitor, Giovanni Filippo Gallarati Scotti, who said about Muscat: ‘Since some time ago, the ministers of this secular government, and especially the principality’s attorney general, seem to have changed their way of thinking.
[...] The new spirit, which began to take hold of this man’s mind with the Grand Master's approval, has come out with various decisions which are offensive to the liberty of the Church’.
The ‘offensive decisions’ which Scotti referred to were the attempts made by Muscat to curb the effective authority of the pope over the jurisdiction and deliberations of the local government.
In fact, Muscat goes on to confirm and further substantiate the claims he had upheld in favour of the sovereignty and independence of Malta’s government in all decisions within his jurisdiction.
Muscat's book, written in old Italian, has 124 pages, and it was published in Rome at the printing press of the Lazzarini family.
[8] The above-mentioned title continues with the words ‘... Suoi Tribunali, Segnatura, e Legisti’ (... its Tribunals, its Secretariat of State, and its Law Consulates).
Muscat composed it in response to a book, called Ragionamenti (Reasonings), by Giandonato Rogadeo, who sustained that the jurisdiction of Malta's government was limited by the supreme authority of the pope and by his institutions.
With frank and candid language, and also with conviction and philosophical clarity, Muscat left no doubt on which side of the fence he stood.
Usually called simply the Codice De Rohan, this book was basically a revision of the entire corpus of laws and legal customs of Malta.
A second publication, issued two years later, in 1786, under the title Bando e Prammatica da Valere in Perpetuo (A Law and Procedure to Stand in Perpetuity), was even more explicit than the Diritto Municipale.
It acknowledged that the prince had the right to sanction or abolish the execution of any legal instrument issued by a foreign authority, including the pope, the congregations of the Holy See, and the Inquisition.
According to him, Muscat was one of "those modern philosophers of Malta" "cui il nome pur solo, e l’ombra della Chiesa, e delle Ecclesiastiche preprogative e invidioso e odiosissimo" (for whom the very name and the shadow of the Church, and of ecclesiastical prerogatives, is detestable and hateful).
A little after the confrontation with the bishop, he informed the inquisitor that henceforth he would not submit any case before the pope, even those related to the faith, without first tendering them to the Grand Master for his approval.
Muscat maintained that the Church could exert its jurisdiction solely in matters pertaining to the sacraments, the faith, morals, and ecclesiastical discipline.
Pope Pius VI threatened de Rohan that, if Muscat was not immediately removed from Attorney General, the Holy See will disband the Hospitaller order.
At one point, he denied the bishop the right to judge a case of divorce since he claimed that marriage was a social contract recognised only by the civil authority.
Later, defending his responsibility in resisting and curtailing the interference of Rome in the affairs of state, he publicly announced the ‘at long last the pope will have to relinquish all [the power] he has’.
This time the inquisitor made sure that neither de Rohan nor his successor as Grand Master, Ferdinand von Hompesch zu Bolheim, would change their mind.
His personality and contribution is all the more intriguing because he hailed from the lower classes of society, and not only made it to the top but also attempted to affect some real change by applying his philosophical knowledge to good effect.
However, much more research work is needed to uncover the lacking documentary evidence which could substantiate the still unknown aspects of Muscat's interesting life, especially those (but not only) related to his last years away from Malta.