The phrase "adequate theory" is grammatically correct and can be used in written English.
You can use the phrase "adequate theory" when discussing a theory that is considered sufficient or satisfactory in explaining a certain phenomenon or concept. Example: After conducting numerous experiments and reviewing various studies, the scientists concluded that the existing theory on the origins of the universe was an adequate theory to explain the Big Bang.
An adequate theory of sensory function implies an adequate theory of brain function.
It has been pointed out that An adequate theory of sensory function implies an adequate theory of brain function.
In recent years there has been little consensus among scholars on an adequate theory, or framework, for explaining or describing ritual.
The most serious difficulty facing Darwin's evolutionary theory was the lack of an adequate theory of inheritance that would account for the preservation through the generations of the variations on which natural selection was supposed to act.
Indeed, despite his own commitment to CRTT as a necessary feature of any adequate theory of the mind, even Fodor doubts that CRTT is by itself sufficient for such a theory.
While the theory of dilute electrolyte solutions is well advanced, no adequate theory exists for concentrated electrolyte solutions primarily because of the long-range Coulomb forces that dominate in ionic solutions.
And an adequate theory of brain function in its turn requires that the nervous system's behavioral repertory be predictably related to the behaviour of the elements that compose it.
I would reverse his argument completely by suggesting that knowledge of the brain is not necessary for an adequate theory of the mind and, ironically, in light of his position, that a knowledge of brain function cannot be obtained without a sound theory of mind and behavior".
An adequate theory of quotation must account for how such dual use and mention is possible.
Surely such knowledge is possible, so an adequate theory of knowledge must accommodate the possibility.
If intuition reveals a plurality of ultimate goods, then an adequate theory must recognize that plurality.
