it seems as though Descartes (once more influenced by ideas from previous philosophical traditions) may have slipped into thinking that an idea of X actually shares X. So an idea of infinity, for instance, would be an infinite idea.
I think this is true. Inasmuch as true infinity cant be conceived; we cant picture in lour minds an inumerable amount of objects; at best we can imagine a series of individual objects or a limited group of them in succession but tgis is not true infinity. Or else we can imagine the idea of negating finitude; we could comment that an object is limited bt tgis is not the same as infinity.
likewisde its true for any x.
I arrived at this comment after reflecting that any thought in our minds is a nmuemonic and neurological analog of an experienced, sensed, object as in the bok to build a mind by ray kurtzweil

