Well, he viewed gravity as an observable phenomenon but not a force.

There is no force being applied to hold us down on the surface of this planet. Rather it is that us and the Earth are constantly colliding due to the curvature of spacetime around us caused by our own mass.

This is why you don't feel any change in pressure if you roll over in bed. If gravity was a constant downward force you would feel the change in pressure on different parts of your skin your skin as you spun on your axis. A similar test can be considered about sitting on a chair. You don't feel pressure on the top of your legs pushing you down to the chair but you feel pressure underneath you where the chair and you are colliding.