Full Idea
For Kierkegaard, reason, which produces only abstractions, negates our individual essence; this essence is subjectivity, and subjectivity exists only in the 'leap of faith', whereby the individual casts in his lot with eternity.
Gist of Idea
Reason is just abstractions, so our essence needs a subjective 'leap of faith'
Source
report of Søren Kierkegaard (Either/Or: a fragment of life [1843]) by Roger Scruton - Short History of Modern Philosophy Ch.13
Book Reference
Scruton,Roger: 'A Short History of Modern Philosophy' [ARK 1985], p.189
A Reaction
Interesting, but this strikes me as a confusion of reason and logic. A logical life would indeed be a sort of death, and need faith as an escape, but a broad view of the rational life includes emotion, imagination and laughter. Blind faith is disaster.