If the idea isn't real what are you talking about? You mean making your ideas come to pass, but the idea itself is real whether or not you fulfill it. And the point was using an analogy "as ideas are real..."
The matter doesn't change...The substance doesn't change
As has been said many times, "substance" here is a term of art; it is not the same as matter.
I have an idea that my truck is a brand new dual wheel F350 but alas, when my head clears, it's the same of clunker than it was before the idea was conceived.
Your truck's matter has changed in some way every single instant that you have had it - from brand new until right now. But it is still your truck, You'd even say "I've had the same truck for five years now. But according to your "idea" of "real" this statement is not true about your truck, because its matter has changed.
What is ownership? What color, weight, smell, taste? If I say, "That truck belongs to the proletariat as represented by the Dear Zero Obamanation," that's just an idea, right? It's not real? And especially it's not any more (or less) real than the idea that it's wrong for me to say or think that?
There's 'really' nothing to disagree about, so if you'll just hand me the keys, I'll be out of your hair.