(1) Consciousness and awareness are essentially synonymous. 

(2) If we expand our notion of "thought" beyond our internal monologue and its outward expression through utterances, there can be no consciousness without thought. 

(3) Higher-order theories of consciousness propose that we are conscious of something when we have higher-order thoughts --thoughts that are about things-- about it. 

What is consciousness? 

Consciousness is awareness. Consciousness of something is awareness of something. An organism without any awareness cannot be thought of as a conscious being. 

While these platitudes surely do well to represent the suppositions of folk psychology, is there any good reason we have to deny their veracity? Surely not.

 From a higher-order theory of consciousness perspective, this is what it means when there is something it is like to be an organism. Are bats aware of their surroundings and themselves? Self-awareness can be as 'primitive' as feeling (being aware of) the pang of hunger and outward awareness as simple as intently seeking food to quell that hunger.

Inasmuch as a creature can have a higher-order thought about something, there is something it is like to be that creature, and therefore, that creature is conscious. 

What are “thoughts” beyond our internal monologues?

Consciousness is constituted by the ability to have thoughts about things --to be aware of one's surroundings, oneself, and the things and beings found in one's surroundings, in a fashion that is ambiguously controllable. But does this mean that consciousness cannot exist without thought?  

Thus, the short answer to this question would be, "no. Consciousness requires thought." 

This is often a jarring conjecture for ordinary people and even philosophers to swallow. The philosopher Thomas Nagel, for instance, certainly does not want to attribute consciousness to bats because he thinks that bats possess thoughts; what it is like to be a bat is so foreign to us that the word “thought” almost seems inappropriate to attribute to bats. While thought seems integral to human consciousness, extrapolating this to consciousness in general –including that of other animals-- feels rather counterintuitive. 

However, such seeming is because “thoughts" are conventionally conflated with our internal monologue and its outward expression through our utterances.

It is unclear whether dogs or birds have an internal monologue because they do not express utterances we can fully understand; and because our brains are egocentrically hard-wired, we tend to surmise on this basis that they lack thought –though, nowadays, few would take this a step further to say that they lack consciousness. And typically, this is because it is clear that dogs and birds possess awareness, but most people do not typically view “awareness” as synonymous with “thinking.” How can "awareness" be a form of "thinking"?

The Higher-Order Thought Theory of Consciousness

Expanding our notion of "thought" to include what philosopher David Rosenthal calls "higher-order thoughts" is a coherent remedy to this common and intuitively-compelling response. In fact, it is probably the most digestible theoretical framework from which to draw in answering whether there can be consciousness without thought, as it expressly grounds consciousness in a special and not-at-first obvious form of thinking.  

Rosenthal’s higher-order thought theory –one among many competing higher-order theories-- states that something is conscious if we have a higher-order thought about it.

Intuitively what comes to mind in response to such an idea is that a little internal utterance needs to be emitted about the things we perceive and experience for them to be conscious. Nevertheless, that is an over-simplification based on an inability to suspend judgment in broadening our notion of “thought.”  

Higher-order thoughts are themselves unconscious, non-inferential (i.e., immediate) states of awareness about things in our experience, which assert that something is the case. They are, therefore, the mental states we possess that are about other mental states, whose contents (outputs) derive from stimuli (inputs) that affect our bodies and brains from the outside world. Whatever is the focal point of importance in your experience at any given moment is what is conscious about your experience.

What it is like to have an experience are the salient features of that experience for the experiencer. And what determines salient features are the things we pay most attention to and our attitudes towards them. Therefore, consciousness is not an intrinsic feature of the mind, but it depends on these crucial relations between one’s awareness, the things one is aware of, and the attitude one brings to bear toward them.

If an organism lacks such relational abilities, it cannot be thought of as conscious, according to Rosenthal’s higher-order thought theory of consciousness.  

The higher-order thought theory is quite easy to prove in humans. One simple way is by having a higher-order thought about a higher-order thought –this, in fact, is what Rosenthal believes introspection is.

For example, if you are looking at a painting, and you utter to yourself, “I am looking at a Monet painting,” and you become immediately aware that you are looking at a Monet painting, you have just become aware of a higher-order thought. What we perceive and give salience to focally is what a higher-order thought is about –and we can come to subjectively be aware of these higher-order thoughts, and this ability for introspection constitutes self-consciousness.

The ease with which this is proved in humans is not found in other animals, who, in large measure, cannot report clearly to us on their mental states. Our self-consciousness drives the egocentric inference from this that other animals lack thought.

Human internal monologue is, for the most part, merely our redundant reiteration of the on-goings of focal experience –uttering to oneself that “I am looking at a Monet painting” is nothing more than self-consciousness, not consciousness in general.

Consciousness does not hinge on human superfluity –quite the contrary, in fact.