In many respects, Watts is the orthodox Locke.
Watts' Logic is clearly influenced by Locke's Essay. In fact, the outline of both works are nearly identical. But it is not how they are alike that matters most - it is how they are different.
1) Unlike Locke, Watts has a doctrine of the fall and acknowledges the limits of reason imposed by original sin.
2) And unlike Locke, Watts has some room for innate ideas, which seemed to be derived from Scripture (Rom. 2).
3) And this seems to suggest that Watts is still operating within the credo ut intellgiam (faith seeking understanding) paradigm, which is a third significant difference.
4) It is also a much shorter and more didactic.
Watts is probably more a child of the Enlightenment than many of his contemporary readers realize. For example, Watts (like Locke) has very little interest in the authority of tradition. But for all his Enlightenment optimism, he still remains within the bounds of orthodox Protestantism, the Trinity Controversy notwithstanding.