Table 1. Modes of learning.

each mode of learning	makes observations...	and combines them...	to inform activities...	...that accumulate into usable knowledge	example
LABORATORY EXPERIMENTATION	controlled observation to infer cause	replicated to assure reliable knowledge	enabling prediction, design, control	theory (it works, but range of applicability may be narrow)	molecular biology & biotechnology
ADAPTIVE MANAGEMENT (QUASI-EXPERIMENTS IN THE FIELD)	systematic monitoring to detect surprise	integrated assessment to build system knowledge	informing model-building to structure debate	strong inference (but learning may not produce timely prediction or control)	Green Revolution agriculture
TRIAL & ERROR	problem-oriented observation	extended to analogous instances	to solve or mitigate particular problems	empirical knowledge (it works but may be inconsistent & surprising)	Learning by doing in mass production
UNMONITORED EXPERIENCE	casual observation	applied anecdotally	to identify plausible solutions to intractable problems	models of reality (test is political, not practical, feasibility)	most statutory policies

Political conflict tends to weigh more heavily than scientific debate as one moves downward in the table. Cf. "Scientific uncertainty can be high so long as acceptability is high." (Walters and Holling 1990, 2067).

Environmental policy has been formulated in response to unmonitored experience (e.g., disappearance of valued species), but environmental management assumes one of the other modes of learning is possible (e.g., maximum sustainable yield).