The issue that vexed Kant was central to what 20th-century scholars called "the philosophy of mind ". The flowering of the natural sciences had led to an understanding of how data reaches the brain. Sunlight falling on an object is reflected from its surface in a way that maps the surface features (color, texture, etc.). The reflected light reaches the human eye, passes through the cornea, is focused by the lens onto the retina where it forms an image similar to that formed by light passing through a pinhole into a camera obscura . The retinal cells send impulses through the optic nerve and then they form a mapping in the brain of the visual features of the object. The interior mapping is not the exterior object, and our belief that there is a meaningful relationship between the object and the mapping in the brain depends on a chain of reasoning that is not fully grounded. But the uncertainty aroused by these considerations, by optical illusions, misperceptions, delusions, etc., are not the end of the problems.
The attempt to rectify the perceived deficiencies of the Philosophic Radicals through engagement with other styles of thought began with Mill’s editing of a new journal, the London Review , founded by the two Mills and Charles Molesworth. Molesworth quickly bought out the old Westminster Review in 1834, to leave the new London and Westminster Review as the unopposed voice of the radicals. With James Mill’s death in 1836 and Bentham’s 1832 demise, Mill had more intellectual freedom. He used that freedom to forge a new “philosophic radicalism” that incorporated the insights of thinkers like Coleridge and Thomas Carlyle. ( Collected Works [ CW ], ). One of his principal goals was “to shew that there was a Radical philosophy, better and more complete than Bentham’s, while recognizing and incorporating all of Bentham’s which is permanently valuable.” ( CW , ).
Kant was only 5 feet tall, thin and of fragile health. Nevertheless, he reached at the time extremely old age which he attributed to his strict daily routine. He got up at 5 o’clock every day and spent the next hour drinking tea, smoking his pipe and meditating. From 6 to 7 o’clock, he prepared for lectures he gave at home until 9 o’clock. He then worked in his study room until 1 o’clock and spent the next three hours dining, usually with his friends. After his only meal, he took a one hour walk and spent the afternoon and evening for reading and writing. The renowned German philosopher was completely dedicated to his work and never married.