He was born in Oban on 27 August 1913, the son of Donald M. MacKinnon, Procurator Fiscal, and his wife, Grace Isabella Rhynd.
He is particularly noted for the depth of analysis he applied to intractable theological problems, not least the refusal to simplify difficult questions in order to produce tidy or conclusive answers.
[10] The label derives from MacKinnon's use of literary, artistic, and political sources in his work – modes of enquiry which operate in contrast to the systematic and epistemologically narrow approach of some theology and philosophy.
[11] The intensity of MacKinnon's thought was matched by his lecturing style, which was marked by "his dangerously strong charisma, his ability to terrify adversaries".
[citation needed] Former students Dame Iris Murdoch, Philippa Foot, and Lord Williams of Oystermouth expressed deep indebtedness and admiration for his input into their intellectual development.
He goes on to argue that it is in keeping with a Kantian metaphysics to deduce God from this sense of awareness: "Kant [is] in the end a theist. ...
[But] we are all the time thrust outside those frontiers, precipitated beyond them by a moral experience on whose formal unity, in the most diverse human situations, Kant insists.
MacKinnon illustrates this with examples of tragedy from Shakespeare, Greek thought, and Jesus' parables, and concludes that "[i]t is as if we are constrained in pondering the extremities of human life to acknowledge the transcendent as the only alternative to the kind of trivialisation which would empty of significance the sorts of [tragic] experience with which we have been concerned".