"No words are oftener on our lips than thinking and thought. So profuse and varied, indeed, is our use of these words that it is not easy to define just what we mean by them."  - John Dewey, How We Think, p. 1

A hundred years after John Dewey wrote these lines, we haven’t come all that closer to an understanding of what thoughts actually are, as is made clear in the title of a recent Psychology Today blog: “What thoughts are remains mysterious from a neuroscientific point of view”.Good ol’ Wikipedia does provide several possible definitions, including:

A single product of thinking or a single idea (“My first thought was ‘no.’”)

The product of mental activity (“Mathematics is a large body of thought.”)

The act or process of thinking (“I was frazzled from too much thought.”)

The capacity to think, reason, imagine, etcetera (“All her thought was applied to her work.”)

The consideration of or reflection on an idea (“The thought of death terrifies me.”)

Recollection or contemplation (“I thought about my childhood.”)

Half-formed or imperfect intention (“I had some thought of going.”)

Anticipation or expectation (“She had no thought of seeing him again.”)

Consideration, attention, care, or regard (“He took no thought of his appearance” and "I did it without thinking.")

Judgment, opinion, or belief (“According to his thought, honesty is the best policy.”)

The state of being conscious of something ("It made me think of my grandmother.")

Tending to believe in something, especially with less than full confidence ("I think that it will rain, but I am not sure.")

So a thought can be a process, the outcome of a process, capacity, inchoate intention, opinion, state of beholding, state of awareness, tentative belief, or an act of contemplation. Is there a common theme to these definitions? Other than the most general, banal, and unhelpful – like thoughts are cognitive processes and their products. Do thoughts actually exist?

Reference:

Dewey, John "What is thought?" Chapter 1 in How we think. Lexington, Mass: D.C. Heath, (1910): 1-13. Accessed on 3/9/14: https://www.brocku.ca/MeadProject/Dewey/Dewey_1910a/Dewey_1910_a.html