The business secretary came under fire earlier this month after proposing to "screen out mediocrity" and "ration research funding by excellence".
At an event organised by the Royal Society at the party's annual conference in Liverpool, he revealed that he had even come under attack from his son - a quantum physicist based in Singapore - over his comments.
However, Mr Cable said that as a government minister in a financial crisis, he had to make decisions to prioritise funding for certain scientific research given the size of the budget deficit.
He cited as one example the ITER nuclear fusion research programme, which drew on a "significant chunk" of science funding even though it was unclear when, or if, any benefits would be reaped.
Mr Cable joked that he was old enough to remember "boffins" on television decades ago suggesting that one day all power would be magically produced through fusion.
Calling on the science community to provide more evidence, he said: "I totally understand why you want to argue 'we want more money', but it would be helpful if we had some kind of indication of what the priorities are."
However, the minister also reassured his audience that theoretical science was important and that he did not believe in funding only research with clear commercial benefits.
"It is an artificial distinction, and we in government don't buy it," he said.
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