Four or five, depending on what fits in the allocated space. Always at least one pair of sandals (this might change come winter), semi-dressy sneakers and dress shoes. Yup, I do dressy events a lot...it's Seattle!
I have a couple more pairs in storage and rotate them. For me the variety makes enough of a tangible difference in my life it's worth the sacrifice in minimalism.
This is my 'shoe drawer'. It came with the van and tucks under the seat completely out of sight. I can keep 3 or sometimes 4 pairs in there, along with some socks and hosiery protected in ziploc bags:
I also tend to keep a pair of whatever sensible shoes I was last wearing tucked away somewhere in or near the footwell of the driver's side, hence the fourth/fifth pair. Since witnessing a few accidents and having a lot of breakdowns with my last van, I've resolved to never again drive barefoot or in nonsensical shoes.
Otherwise I'm barefoot whenever I get the chance! No slippers for me; all shoes stay in the front and their purpose is to put on before I exit the van or for driving.
A pair of sandals, two pair of ratty tennis shoes and two pair of nice tennis shoes. Barefoot is awesome in the van and at the beach. I have more hats than I do shoes.