What did Kierkegaard mean by a leap of faith, and why did he link anxiety to freedom?

For Kierkegaard, a leap of faith means committing yourself to something that no amount of evidence can settle, and anxiety is what we feel when we realise we are free to choose. Strangely, the Danish philosopher never wrote the phrase 'leap of faith' himself. The idea is commonly attributed to him, but he spoke of a qualitative leap: a change from one quality, or state, to another, which he wrote can take place only by a leap.

Kierkegaard, widely considered the first existentialist philosopher, lived the problem he wrote about. In 1841 he broke off his engagement to Regine Olsen, though the two are generally believed to have been deeply in love. In his journals he blamed his melancholy, but his precise motive remains unclear.

In Fear and Trembling, published in 1843 under a pseudonym, he looked at the Bible story of Abraham, who is told by God to sacrifice his son Isaac. Tragic heroes such as Agamemnon, Jephthah and Brutus, who sacrificed or punished their children, did so for a purpose their communities could understand. Abraham's act, in the book's argument, serves no purpose for a nation, community or public vow and makes no sense to a rational system of ethics. That is why faith, for Kierkegaard, is something beyond ordinary reasoning.

One line in the literature sums up his view of commitment: no evidence could ever completely justify total religious or romantic commitment, and faith means making the commitment anyway. He added that having faith means having doubt too, so the believer is never simply certain.

Then comes anxiety. In The Concept of Anxiety he argued that it informs us of our choices, our self-awareness and our responsibility. It is not only a bad feeling: it is the signal that we are free.