Imagine Jane says: “I think that using cat treats as a basis of currency is a fundamentally flawed idea- and it is my strong belief that this is an idea that was introduced by cats.”
And then Jack says later: “I think that using cat treats as a basis of currency is a fundamentally flawed idea- and it is my strong belief that this is an idea that was introduced by cats.”
Of course that isn't okay! Wouldn't Jane say something? It's a lot harder to claim someone's idea as your own when you are at the same fancy party as them!
Jack should have given Jane credit for the whole phrase. That includes putting quotes around the entire phrase he borrowed word-for-word if in writing.
What if Jack instead tries: “What a fundamentally flawed idea using cat treats as money is! Clearly, this is an idea introduced by cats and being pushed by the Big Kitty lobby.”
“The thought of using the cat treat as legal tender is a preposterous, ludicrous one. Evidence seems to point that the beneficiary of such a proposal- the cat- put forward the idea.”