Hilary (ca 300-368) was born in southwestern Gaul.  His parents were pagan and gave him what must have been an excellent classical education, to judge by the good Latin style of his later writings.  He also knew Greek, learned in part during his exile in the eastern part of the empire.  He was baptized, along with his wife and daughter, at a relatively mature age, and was elected bishop by the inhabitants of Poitiers only a few years later.  He quickly became embroiled in a theological dispute with adherents of Arianism, which was still vigorous despite its condemnation by the Council of Nicea.  Hilary fell afoul of the emperor Constantius, who was somewhat "soft" on the heresy, and was exiled to Phrygia in Asia Minor for several years.  After his return to Poitiers he completed De Trinitate, his major work, and mentored the great monastic Martin of Tours. 

Edward C Sellner, in Finding the Monk Within (HiddenSpring, 2008, pp 64-66) has some good insights into Hilary's approach to the Christian faith.

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All of his works...were composed with the strong conviction that God was not only one being, but three persons...God, and those who are created in God's image, Hilary believes, are thus called to community, to participate and build in their own lives communities that reflect the God in whose image they have been made...

A second conviction...is his intense love of and loyalty to Jesus Christ.  For Hilary, the Son of God was truly God not in name and metaphor only, but in the fullest sense and deepest reality.  This personal relationship with Christ, in fact, is his primary motive for the writings on faith that he does.  It is his reading and study of the sacred texts of scripture that inform his theology and the explanations he gives to justify belief in the power and equality of the Trinity.  Ultimately his love of Christ relies not solely on intellect and intellectual arguments, but upon his intuitive senses, his heart...

Hilary also learned from the Eastern fathers during his exile that to be a theologian was, above all, to be a person of prayer.  They had taught him that all theology begins and ends in prayer.  With this awareness, it was natural for him to conclude that "God cannot be known except by devotion".  As he writes in his book on the Trinity, "What presumption to suppose that words can adequately describe God's nature, when thought is often too deep for words, and His nature transcends even the conceptions of thought...We must believe, must apprehend, must worship, and such acts of devotion must stand in lieu of definition."  For Hilary, what he learned from the Eastern fathers was the ancient Christian principle, lex orandi, lex credendi" (the law of worship is the law of belief); in other words, how a person or community worships reveals what an individual or a community believes.  Thus his understanding of faith is linked intrinsically with a life of prayer, one that includes the reading of scripture, yes, but also public worship and personal prayer...

A fourth element of his theology also reflects the teachings of the Eastern father...when Hilary says, "What presumption to suppose that words can adequately describe God's nature."  Eastern theologians had taught him this apophatic theology:  based upon the presupposition that words or dogmatic definitions cannot fully explain the profound mystery of God.  Here Hilary anticipates the theology of later Eastern Orthodox Christians, the sixth-century writer Pseudo-Dionysius, and a number of medieval mystics, including the fourteenth-century anonymous English author  of the Cloud of Unknowing and the sixteenth-century Spanish poet, John of the Cross (1542-1591).  Hilary states in his book on the Trinity that the very "purpose" of faith, what it proclaims, is that it cannot fully "comprehend that for which it is seeking".  Anything that is said is merely an attempt to wrap words around a mystery that is beyond verbal or intellectual explanation.