Also F. H. Bradley, Appearance and Reality, p. 346:
The first part of Eliot's note draws from Canto 33, lines 46-47, of Dante's Inferno:
The speaker is Count Ugolino, an Italian nobleman. A rival captured Ugolino, along with his sons and grandsons, and imprisoned them in a tower. The tower was locked and the count and his family were left to starve. For a brief overview of The Divine Comedy, see the note to the dedication.
The second part of the note is a quote from the British philosopher F. H. Bradley. Bradley's Appearance and Reality argues that each person's experience of the world is unique and that communication between people is therefore fundamentally ambiguous. Bradley was the subject of Eliot's abandoned dissertation work.