Insanity is often the logic of an accurate mind overtasked.

Holmes’s aphorism reframes “insanity” not as mere irrationality but as a grim byproduct of excessive mental strain. The phrase “logic of an accurate mind” suggests a person whose reasoning powers are strong and systematic; when such a mind is “overtasked,” its very rigor can harden into fixed ideas, obsessive patterns, or delusional conclusions that follow an internal logic. The line also reflects a 19th‑century interest in the borderlands between genius, nervous exhaustion, and mental illness, implying that breakdown can be continuous with ordinary cognition rather than its opposite. It cautions against romanticizing mental collapse while acknowledging how pressure can deform even sound intellect.