He is known for his anti-evolutionist positions, also publicised in institutional circles, for his critique of relativism and the lines of thought established in the Catholic Church after the Second Vatican Council.
[7] In fact, Professor de Mattei was one of the first critics of Pope Francis to whom he dedicated the 11 February 2014 article "Motus in fine velocior" in Corrispondenza Romana.
[8] Among the various initiatives of criticism is also the Correctio Filialis De Haeresibus Propagatis,[9] a 25-page letter written on 16 July 2017 and signed by 40 Catholic priests and lay scholars, sent to Pope Francis on 11 August 2017.
[11] Conservative Catholic historian Archbishop Agostino Marchetto described it as an "ideological and hyperbolical work", which represents the opposite side of the School of Bologna, paradoxically coming to the same conclusion, i.e. that Vatican II was a break in the Church tradition;[16] Italian sociologist of religion Massimo Introvigne (who is himself a member of the traditionalist group Alleanza Cattolica) denounced it as "following a critical method which devaluates the texts of the Conciliar documents".
[17] With the Lepanto Foundation, Professor de Mattei organised events called Acies Ordinata: the first in Rome on 19 February[18] and 28 September 2019,[19] the last in Munich on 18 January 2020.
At the last event, among others, Archbishop Carlo Maria Viganò[citation needed], Michael Matt, editor of the American newspaper The Remnant; Alexander Tschugguel, the young Austrian known for having thrown the Pachamama into the Tiber[citation needed]; John-Henry Westen – editor of the international website LifeSiteNews; John Smeaton – president of the Society for the Protection of the Unborn Children (UK); Baroness Hedwig von Beverfoelde, German pro-life leader; German writer Gabriele Kuby, Count Peter zu Stolberg; Prof. Thomas Stark; Dr Thomas Ward, president of the British Catholic Doctors.
[23] When the Russian-Ukrainian conflict began on 24 February 2022, Professor de Mattei took a stance opposing the pro-Russian narrative, distancing himself from other traditionalist Catholics who sided with Vladimir Putin, including Archbishop Carlo Maria Viganò.
[24] De Mattei's perspective on the conflict is not limited to geopolitical aspects, but he rather believes that the key of interpretation for such dramatic events is the message of Fatima, as he recently stated.
[25] In this regard, Professor de Mattei considered valid the Consecration, made by Pope Francis on 25 March 2022, of Russia and Ukraine to the Immaculate Heart of Mary according to the dictates of Our Lady in the 1917 apparitions in Fatima.