Luckily (for them and for us), their conclusions proved to be mere speculation.

Anyway, mere speculation, all of that.

In order to satisfy that stringent test, evidence was required, not mere speculation, and that evidence would be subjected to rigorous examination.

Many are still in the early planning stages, or even mere speculation, as with the transatlantic tunnel.

Moral inquiry, within the present context, means inquiry into practical matters (as opposed to mere speculation or scientific inquiry).