Grammatical rules are discrete, not weighted, and not vulnerable

The paper defends the following positions: Grammaticality and acceptability must not be regarded as virtually coextensive. Grammaticality is discrete; acceptability is gradient. Acceptability can be measured directly; grammaticality can only be tested indirectly. Acceptability is a reflex of performance factors interacting with the mentally represented grammatical rule system; grammaticality is a theoretical concept. Acceptability is a theory-independent behavioral property; grammaticality is defined by the cognitively encapsulated grammar, which is the empirical research target of grammar theory.