 Even in the context of trying to explain what the autonomy thesis is, Newmeyer (1991: 3) talks about five formulations of the thesis, each of which can be found in some Essentialists’ writings, without (apparently) realizing that they are non-equivalent. One is the relatively strong claim that the central properties of linguistic form must not be defined with essential reference to “concepts outside the system”, which suggests that no primitives in linguistics could be defined in psychological or biological terms. Another takes autonomy of form to be a normative claim: that linguistic concepts ought not to be defined or characterized in terms of non-linguistic concepts. The third and fourth versions are ontological: one denies that central linguistic concepts should be ontologically reduced to non-linguistic ones, and the other denies that they can be. And in the fifth version the autonomy of syntax is taken to deny that syntactic patterning can be explained in terms of meaning or discourse functions.