While one finds company in himself and his pursuits, he cannot feel old, no matter what his years may be.

Alcott links “old age” less to chronology than to inward vitality. If a person can be companion to himself—able to dwell contentedly in his own mind—and remains engaged in meaningful “pursuits” (study, moral self-culture, creative work), then the usual markers of aging lose their power. The line reflects a Transcendentalist emphasis on self-reliance and the sustaining resources of the inner life: solitude becomes nourishing rather than impoverishing. It also implies that feeling old is often a symptom of boredom, dependence, or loss of purpose; continued curiosity and self-directed activity preserve a sense of youthfulness even as years accumulate.