Full Idea
The 1924 idea of the 'probability wave' meant a tendency for something. It was a quantitative version of the old concept of 'potentia' in Aristotelian philosophy ...a strange kind of physical reality just in the middle between possibility and reality.
Gist of Idea
A 'probability wave' is a quantitative version of Aristotle's potential, a mid-way type of reality
Source
Werner Heisenberg (Physics and Philosophy [1958], 02)
Book Reference
Heisenberg,Werner: 'Physics and Philosophy' [Penguin 1989], p.29
A Reaction
[compressed] As far as I can see, he is talking about a disposition or power, which is exactly between a mere theoretical possibility and an actuality. See the Mumford/Lill Anjum proposal for a third modal value, between possible and necessary.
Related Idea
Idea 17535 Dispositionality has its own distinctive type of modality [Mumford/Anjum]