[jballanc]

Falsifiability is a feature of every element of science. Something that is not falsifiable isn't science. Period.

But a Theory is not a guess. It is a framework built from individual pieces, some of which may be hypotheses (effectively guesses) that have been tested and found to hold within the larger structure of that framework.

[aortega]

If you are based in individual pieces that may be effectively guesses, how you are not also a guess?

[jballanc]

Try formulating your question again, but this time don't leave out the part where I wrote "that have been tested and found to hold".

[chc]

Because you have been tested. The term "guess" implies lack of good grounding.