وثانيها: ما يمكن أفراده ولم توجد، كالعنقاء وجبل من الياقوت
Second are concepts whose instances could exist but do not actually occur, such as the ʿanqāʾ and a mountain of ruby.
“A mountain of ruby” combines intelligible descriptions; the concept does not immediately entail a logical contradiction preventing any conceivable instance.
The book's ʿanqāʾ example illustrates the distinction between logical possibility and an imagined or unverified external referent; it is not evidence that such an animal actually exists.