Olivier Messiaen's principal theological themes in the Meditations are directly related to the monotheistic but Trinitarian notion of God. Messiaen's stated aims for his music clearly follow the threefold pattern: he constantly declared his work to be spiritual sacrifice, and his music became testimony to his loyalty in the ordinary world by asserting publicly and repeatedly his unwavering faith. Messiaen's endeavour is not evangelism in the sense of a zealous effort to convert people to Catholicism, but evangelism in its literal meaning of 'spreading the gospel'. Messiaen's theology is one of joy and light, salvation and glory; interestingly, it embodies nothing that is anti-Catholic, innovative or even daring. According to Messiaen himself, three principal theological topics are expressed in his music: God's love, human love, and God's creation. Thomas Aquinas is recognized by the Catholic Church as its most important Western philosopher and theologian. Messiaen was clearly strongly influenced from a young age by Aquinas's writings.