Leftow's research interests include metaphysics, medieval philosophy, and philosophical theology.[3] He proposed the so-called "Latin Trinity", which examined the tradition of Latin theories involving the Trinity. He likened this to an individual performing three roles, three events, and three time streams that are distinct for such individual but they occur simultaneously for others.[4] Leftow has focused on the works of Thomas Aquinas, drawing from his arguments to theorize on God's omnipresence.[5] On this subject, he noted that there is widespread consensus that God is eternal but there are disagreements regarding what it means.[6] Leftow is also credited for proposing an explanation about the constant change in God prior to creation - that "God can delay creating to enjoy anticipating a universe and/or desiring to create one."[7]
Matter, Parts and Number: Aquinas' Philosophy of Mathematics. Oxford, forthcoming.
"Anti Social Trinitarianism," in Steven Davis and Daniel Kendall, eds., The Trinity. New York: Oxford University Press, 1999.
"The Eternal Now," in Gregory Ganssle and David Woodruff, eds., God and Time. Oxford: Oxford University Press, 2002.
"Necessary Being", and "Concepts of God," in The Encyclopedia of Philosophy. London: Routledge Press, 1998.
"Anselm on the Cost of Salvation," Medieval Philosophy and Theology. 1997.
"Eternity," in The Cambridge Companion to Philosophy of Religion, ed. Philip Quinn and Charles Taliaferro. Cambridge: Cambridge University Press, 1997.
"Divine Action and Embodiment," Proceedings of the American Catholic Philosophical Association, 1997.
"Can Philosophy Argue God's Existence?" in The Rationality of Belief and The Plurality of Faith, ed. Tom Senor. Ithaca, NY: Cornell University Press, 1995.
Time and Eternity. Ithaca, NY: Cornell University Press, 1991.
^McCall, Thomas (2010). Which Trinity? Whose Monotheism? Philosophical and Systematic Theologians on the Metaphysics of Trinitarian Theology. Grand Rapids, Michigan: Wm. B. Eerdmans Publishing. p. 111. ISBN9780802862709.
^Taliaferro, Charles; Meister, Chad (2010). The Cambridge Companion to Christian Philosophical Theology. Cambridge: Cambridge University Press. pp. 51–52. ISBN9780521514330.