Descartes's rhymes with:
carts, kartes, art's, arts, artz, bart's, barts, bartz, carts, charts, dart's, darts, departs, hart's, harts, hartz, heart's, hearts, imparts, k-mart's, kartes, mart's, marts, martz, part's, parts, parts', schartz, smarts, spartz, starts, tarts, upstarts
Descartes's sounds like:
datacards, decurtis, degrades, descartes, desecrates, deserts, desserts, diacritic, discards, discredits, djakarta's