[Thomas Aquinas’] teachings constitute a complete system, which is why, as ‘Thomism’, they provide the Roman Catholic Church with its philosophy, whose official status was further confirmed by Pope Pius X in Doctoris Angelici (June 1914): ‘The capital theses in the philosophy of St Thomas are not to be placed in the category of opinions capable of being debated one way or another, but are to be considered as the foundations upon which the whole science of natural and divine things is based; if such principles are once removed or in any way impaired, it must necessarily follow that students of the sacred sciences will ultimately fail to perceive so much as the meaning of the words in which the dogmas of divine revelation are proposed by the magistracy of the Church.’ This places Thomistic philosophy and theology above all debate, which – at least in the case of philosophy – is precisely contrary to what philosophy should be.
A. C. Grayling, “The History of Philosophy”, pp. 157