Full Idea
I also count as mere appearances, in addition to [heat, colour, taste], the remaining qualities of bodies which are called primariae, extension, place, and space in general, with all that depends on it (impenetrability or materiality, shape etc.).
Gist of Idea
I count the primary features of things (as well as the secondary ones) as mere appearances
Source
Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 289 n.II)
Book Reference
Kant,Immanuel: 'Prolegomena to Any Future Metaphysic', ed/tr. Lucas,Peter G. [Manchester UP 1971], p.46
A Reaction
He sides with Berkeley and Hume against Locke and Boyle. He denies being an idealist (Idea 16923), so it seems to me that Kant might be described as a 'phenomenalist'.
Related Idea
Idea 16923 I admit there are bodies outside us [Kant]