The Principle of Contingent Causation: The Impossibility of Infinite Regress.

[Loaded dice]

I can conceive of a square circle provided it is placed correctly in a specific non-Euclidian space.  Is it possible?  I don't know.  I'm not sure conceiving tells us much one way or the other.

The classical problem of squaring a circle is impossible in euclidian spaces. If you change the space, you change the problem.

And, for the record, it is possible to square a circle in some non euclidian frameworks.

Unless you can conceive of how something is logically possible, I don't think you've truly conceived of it in any logically meaningful sense.

Not necessarily. People conceived of airplanes centuries ago, without knowing how to make them. And still, no one can deny that it's thanks to their wild dreams and ambitions that we have airplanes today.