Meaning of “the first forty years of life furnish the…”

Counsels and Maxims, T. Bailey Saunders translation; Project Gutenberg #10715. The statement belongs to Schopenhauer’s broader, characteristically pessimistic discussion of age and experience.

The Life of Reason, Reason in Common Sense; the sentence follows Santayana’s discussion of memory and historical learning.

Democracy and Education (1916), Chapter XI, “Experience and Thinking.” Dewey describes experience as a relation between doing and undergoing consequences, then immediately qualifies the active-passive formulation by saying that valuable experience includes cognition insofar as relationships and continuities are perceived. Verified against Project Gutenberg #852 and the scan-backed Wikisource Chapter XI transcription. The sentence is not a denial that cognition matters and is not presented as modern neuroscientific evidence.

Jo's Boys; the reassurance follows a setback and reframes a difficult year as experience that may later prove unusually helpful rather than simply wasted time.

The Autocrat of the Breakfast-Table, represented by Project Gutenberg #751. The line is spoken in Holmes’s table-talk authorial persona and followed by an Alpine image; it is a literary metaphor for intellectual expansion, not a neurological claim.

The Wisdom of Life, T. Bailey Saunders translation; Project Gutenberg #10741. The wording belongs to Schopenhauer’s contrast between intellectual and ordinary forms of leisure.