But it is a start that plays down the complications of learning about gender and discrimination outside the family, in order to produce a viable psychological theory.

The calcichordate theory is not widely accepted as a viable theory on the origins of the chordates.

However, certain features can be expected to be present in any viable theory.

Therefore it is impossible to disambiguate between all viable theories.

"I think that's a very viable theory," a senior government official said.

For several years he was one of the very few physicists who pursued string theory as a viable theory of quantum gravity.

At present, every viable theory of long-term memory involves changes in the structure and protein content of neurons.

There are many viable theories of how the Earth came to acquire its Moon, reflecting the considerable uncertainty as to how it actually happened.

Nothing else will do, so goes a theatrically viable theory.

Duncan needed details if his current line of thinking would pan out into a viable theory.