I'm a bit confused. I'm reading The Philosophy Book, and it mentions a quote on reality, seemingly attributing it to Kant. I cannot, however, for the life of me find a source for the quote outside of this book. Is this just an example given over to help the reader understand, and if so, why is it stated like a quote? Is there another philospher who said this? I'm genuinely confused.
Here's the quote. I've bolded the part I can't seem to source.
Immanuel Kant objected that the argument treats existence as if it were an attribute of things—as if I might describe my jacket like this: “it’s green, made of tweed, and it exists.” Existing is not like being green; if it did not exist, there would be no jacket to be green or tweed.
Any leads would be helpful. Thanks!