**1. Euclidean: Basic principles are **

clear and precise and consistent

with one another; examples:

Euclidean geometry, classical

mechanics, von Neumann’s

quantum mechanics.

2. Heuristic: Basic principles

are clear and precise but

inconsistent with one another;

examples: chess strategies,

legal systems, expert systems

in A.I. using non-monotonic logic.

3. Intuitive: Basic principles

don’t exist or are ineffable

or tacit. Mastery usually involves

apprenticeship, imitation,

massive practice; examples:

philosophy, mathematics, science,

carpentry, language, chess-

almost all human skills!