I think what Jaster is saying is that subjective experience is a
primary knowledge i.e. we experience things (e.g. pain or colour or fear (or God?)) directly, and therefore there is little doubt of its existence for the person experiencing it.
(Quote from
Wiki on Empiricism)
"Objective" knowledge, is secondary, in that it is derived or deduced from our sense experiences but can never be known directly. There are therefore serious questions as to whether our scientific models are reality, or just a way of interpreting our experiences.
Thomas Nagel's book called "
The View form Nowhere" is so called because that is the "objective" viewpoint of science. Nagel points out that while this viewpoint works well for constructing scientific models, it is never complete. In terms of deciding how to live a meaningful life, personal experience and the subjective viewpoint are essential components. Heidegger blamed the alienation we have from nature, the environment etc. on our "view from nowhere" scientistic view of reality.
If you want to see the effects of our "paradigm", contrast our culture with that of the Australian Aborigine, who regards himself as
belonging to the land, not the other way round. His worldview is not "objective", it relates him intimately and personally to his world. This ensures he cares and looks after his environment as the land is like his Mother. We, on the other hand who have objectified the world, as a consequence regard it as simply an exploitable resource. The result is environmental disaster.
So, our objective scientific view of reality is not "Truth". It is a way of interpreting our observations (Kuhn's "scientific paradigm"). What it leaves out as a total worldview is our personal subjective experiences, which is what makes life meaningful for most of us. Sartre was saying this when he stressed the importance of "being-for-itself", as Heidegger did "being there".