The part of a sentence "the assumption underlying" is grammatically correct and commonly used in written English.
It can be used when discussing a statement or argument that is based on a particular assumption. Here is an example sentence: "The economist's analysis was built upon the assumption underlying the theory of supply and demand."
What about the assumption underlying the proposal, that a college education makes a person more employable?
But the assumption underlying that question – that China is now the global economy's weakest link – is highly suspect.
The assumption underlying the Obama policy, critics say, is that all lobbying is suspect, even legitimate advocacy at the heart of a democratic process.
The assumption underlying this statement is that measures promoting environmental sustainability inevitably yield a net economic cost rather than a profit.
They may take what appears to be altruistic positions to improve their public image, but the assumption underlying those actions is that they will increase future profits.
The assumption underlying your Jan . 18front-page article "Doctors Eliminate Wrinkles, and Insurers" is that the overarching motivation of all doctors is greed.
The assumption underlying the drive to full disclosure of our own and others' inner lives is that we should know everything.
But more recently, some health care safety experts have begun questioning the assumption underlying the report's conclusions: that only health care systems, and not individual clinicians, could be held accountable for medical mistakes.
The blame was annoying — some European governments had cut aid to Rwanda — but what really angered Kagame was the assumption underlying that blame, that Nkunda was the big problem in eastern Congo.
The assumption underlying all this is that the military are essentially a social group--an independent source of power and influence--that has to be courted, placated, appeased, bargained with, understood.
The assumption underlying these ventures - private park with a Shakespearean actor brooding over a fountain; private club devoted to the arts - is this: by and large, Americans are very, very stupid.
