Influenced by the art-historical methods of the European-Jewish exiles — Walter Friedlaender, Rudolf Wittkower and Johannes Wilde — who in the 1930s had come to the Courtauld Institute where Blunt was a prominent lecturer, all his books emphasised the dominant ideas that had influenced the artists' work: "In order to appreciate [Poussin] as an artist it is essential to understand the intellectual climate in which he worked and the ideas — religious, philosophical or aesthetic — in which he believed and which affected his method of work as well as his paintings." Poussin's emphasis on clarity, logic and order were similar to the philosophical method and ideas of his close French contemporary René Descartes (1596-1650), whom Blunt only briefly mentions.

Blunt devoted a whole chapter to Poussin's Stoicism — his rationality, scepticism, repression of emotion and self-abnegation — which he himself admired, tried to emulate and desperately needed to sustain him after he was publicly exposed as a spy in 1979. Like Blunt, who had tried to escape from his treacherous past, Poussin told a friend, "my nature compels me to seek and love things which are well ordered, fleeing confusion, which is as contrary and inimical to me as is day to the deepest night." When Poussin failed as a court painter (as Blunt finally failed as a spy) Blunt praised him for preferring "to live apart from the world of public affairs" and in his last years to "become even more completely detached from the world". Blunt's disappointing description of Poussin's penetrating self-portrait (1650) missed a promising opportunity to analyse his complex character: "It is not a lovable face, and that hardness which appears in Poussin's thought is to be seen in the frowning wrinkles of the brow. The mouth is set, and the eyes stare piercingly and almost threateningly at the spectator."

When describing Poussin's qualities as a painter Blunt conceded his weaknesses, but gave these traits a positive interpretation. He stated that Poussin's compositions are simple and static, and have "no surprises, but lead the spectator . . . by a series of visible — one could almost say predictable — steps to a conclusion which seems inevitable from the beginning". Ignoring Poussin's froideur, detachment and lack of human drama, Blunt claimed that "he works out carefully planned, motionless compositions made up of rocklike figures who gaze into infinity, unaware of what is going on around them. His paintings . . . embody an absolute refusal to make any concession to the senses."

Blunt wrote that the Massacre of the Innocents (late 1620s) — which he would later compare to Picasso's Guernica — "shows the whole tragedy [in Matthew 2:16] concentrated in a single group of mother, child and soldier, an almost Racinian concentration". But Walter Friedlaender, to whom Blunt paid tribute in his preface as the great pioneer "who laid the foundation of Poussin studies", echoed Ruskin by stating that in this lifeless painting "the cruelty and terror are static . . . The face of the desperate mother is frozen in terror, like a theatrical mask." In an unconvincing attempt to achieve a synthesis, Blunt endowed Poussin with diametrically opposed qualities, and claimed that he was both impersonal and emotional, rational and mystical. Another forced use of the qualifier "almost" (as in my three previous quotations) undermines the weak argument: Poussin "created paintings which, though impersonal, are also deeply emotional and, though rational in their principles, are almost mystical in the impression that they convey". Despite Blunt's crude distortions and special pleading, his views have prevailed in the modern era. As his former pupil Christopher Wright notes, "so much of the writing on Poussin consists of undeviating admiration."