Our mental states can be divided into two groups, conscious states and inconscious(or unconscious) states. In contrast to creature-consciousness which is ascribed to a subject, it is state-consciousness which is ascribed to mental states. This paper examines three philosopher's theories on the nature of state-consciousness. Rosenthal thinks that a mental state becomes conscious by its being the object of higher-order thought. Lycan thinks that consciousness is a perception-like second order representing of our own mental states and events. According to Dretske, what confers state-consciousness on our mental state is the role it plays in making the subject conscious of some thing or fact. This paper examines Dretske's criticism on the higher-order theories of consciousness by Rosenthal and Lycan, and their respective responses to this criticism. I argue that Rosenthal's position is vulnerable to Dretske's attack, whereas Lycan's is not.