What book by Kierkegaard did Bohr send his brother as a birthday gift in 1909?

In 1909, Niels Bohr sent his brother Harald Kierkegaard’s *Stages on Life’s Way* as a birthday gift.

The choice reflected Bohr’s serious early interest in Søren Kierkegaard, the 19th-century Danish philosopher whose writings explored aesthetic, ethical, and religious ways of living. Bohr read the book while preparing for his master’s examinations and praised it warmly in the accompanying letter.

Bohr admired Kierkegaard’s language and literary style, but he did not accept all of Kierkegaard’s philosophical or religious conclusions. That distinction matters: the gift documents Bohr’s intellectual engagement with Kierkegaard, not complete agreement with him.

A common mix-up is with *Either/Or*, another famous Kierkegaard work and one of the listed alternatives. *Fear and Trembling* and *The Concept of Anxiety* are also Kierkegaard titles, but the 1909 birthday gift was specifically *Stages on Life’s Way*.