Full Idea
I cannot say I am simply thinking but not thinking about anything.
Gist of Idea
All thinking has content
Source
William Lyons (Approaches to Intentionality [1995], Intro)
Book Reference
Lyons,William: 'Approaches to Intentionality' [OUP 1998], p.2
A Reaction
Hard to disagree. However, I can plausibly reply to 'What are you thinking?' with 'Nothing', if my consciousness is freewheeling. Utterly disconnected content isn't really what we call 'thinking'.