I don't see how this account can be right. If I am in a vehicle that accelerates powerfully and if I am leaning forward with my body out of contact with the seat, I am pushed back into the seat.

Likewise if I jump off a cliff I will as though I am being inexorably pulled down, although I am not in contact with the Earth at all. — John

Your body is actually at rest and it is the seat that accelerates forward towards you. Imagine that you are in a motionless rocket in space with you also floating motionless in the middle of the rocket. If the rocket suddenly accelerates forward, you might report that you fell or were pushed to the floor. But it is the rocket floor that caught up with you, not a force pushing you towards the floor. That's why it's called a fictitious force.

This is also true if you jump off a cliff. If you were wearing an accelerometer, it would measure zero. Nothing is pushing or pulling you down. Whereas an accelerometer on the ground would measure an upward acceleration of 9.8m/s/s. So gravity, understood as a force, is also fictitious. The ground's acceleration is explained by spacetime curvature.

But you are making my original point for me very well, which is that there is a disjunct between the phenomenological, 'lived' experience of feeling your body pushed back into the seat and the scientific explanation which relegates the lived experience to the status of being "fictitious". The point is that we experience our body being pushed back and we do not, and cannot, experience the seat accelerating forward to meet our bodies.

The scientific explanation does not relegate our lived experience to the status of "fictitious" (how could it?) It relegates a particular scientific explanation (a reversed effective force) to the status of "fictitious".

Since nothing pushes us back in the accelerating car scenario, it cannot be the case that we experience being pushed back. Our lived experience is real and happens in the world (whatever the correct explanations turn out to be) but our report or explanation of our experience may be mistaken in any given instance.

This is an account in ordinary language terms. There is no need to invoke a manifest/scientific distinction nor to necessarily privilege scientific explanations over any other kind of explanation.

But the fact remains that we feel something pushing us back, and that is the experience we have; it is certainly not a scientific theory, fictitious or otherwise.

We don't. That's a mistake. Though we may think we feel something pushing us back.

There may be, per scientific theory, no force pushing us back. Nonetheless we feel pushed back.That feeling of being pushed back is the lived experience. The explanation is irrelevant to the character of the lived experience.

The difference the distinction is based uoon is between whatever (fallible) theory we may hold to explain the experience and the lived experience itself. You apparently want to dissolve that distinction. That would be to the impoverishment of our experience, in my view, so I cannot recommend it.

Then you're really talking about how your experience seems to you which I agree doesn't commit you to any particular explanation. It does feel like we're being pushed back in the seat and that is consistent with the explanation that the seat is actually accelerating us forward.

My point is that lived experience happens in the world. It is not limited to what it feels like but also includes its physical instantiation (whether recognized by us or not).

I think we're basically in agreement here; it's probably more of a terminological issue.
:)

That latter may well sum up philosophy. :-)

OK, so to connect this back to an earlier point: Our experience of feeling like we're being pushed back in the seat just is our experience of the car's forward acceleration. The only issue is one of knowledge (or awareness) of the correct explanation. We might instead explain our experience in terms of an invisible force pushing us backward, which would be incorrect. (Although we may choose to model it as a fictitious force for instrumental purposes.)

Similarly with gravity. We feel like we are being pushed (or pulled) down by something. That just is our experience of the ground's upward acceleration. Which, in turn, just is our experience of spacetime curvature.