New Delhi, May 24 -- Immanuel Kant is best remembered for philosophical works so dense and demanding that generations of university students have lost sleep wrestling with them. The Critique of Pure Reason, published in 1781, is the kind of book that sits on shelves more often than it is read. His writings on metaphysics, epistemology and moral philosophy reshaped the foundations of Western thought so profoundly that scholars are still unpacking them more than two centuries later.

And yet, tucked inside one of history's most formidable intellectual legacies is a definition of human happiness so disarmingly simple it stops you mid-scroll.

The 18th-century German philosopher, who was born in Konigsberg in 1724 and rarely travelled more th...