Physical Necessity or Deeper Law
The Explanation
Modern physics contains quantities whose measured values are entered into our theories rather than derived from a deeper principle. It is possible that a more fundamental theory will eventually explain why some of those quantities have the values they do.
If apparently independent constants turn out to be connected by deeper laws, some examples of fine-tuning could disappear or change substantially. What presently looks like a narrow selection from many possibilities might instead follow necessarily from more fundamental physics.
Supporting Evidence
The history of science gives good reason to remain open to deeper explanations. Quantities and phenomena once treated separately have sometimes been unified by more comprehensive theories.
Research into alternative universes also shows that physical parameters should not always be varied one at a time. Relationships among parameters can substantially change which combinations remain viable.
Limitations
No presently established fundamental theory derives all of the relevant constants and initial conditions in a way that eliminates the fine-tuning question.
There is also an important difference between demonstrating that a value is physically necessary and merely hoping that a future theory will eventually demonstrate it.
Questions That Remain
Will future physics show that the life-permitting structure of the universe follows necessarily from deeper laws? If so, why do those deeper laws themselves have a structure capable of producing complex matter and life?
Intelligent Design Response
Intelligent Design does not require every physical constant to be independently adjustable. If deeper laws explain some present examples of fine-tuning, those examples should be revised or abandoned.
The design question would then move to whatever level remains unexplained: whether the deeper physical structure itself displays an arrangement that reasonably suggests purpose.