Although there is a sort of empiricism that insists only that human knowledge begins in what can be discerned by the nervous system, modern Empiricism sees all knowledge as limited to what can be discerned by the nervous system. Because of this, Empiricism defines itself as materialist since the nervous system is material and Nominalist since it is particular. One of the most forceful ways to read Berkeley, however, is as giving a very convincing proof that these two aspects of Empiricism are incompatible and that we must choose either the one or the other. Berkeley opts for Nominalism, since he thought (reasonably enough) that the individual character of our knowledge – its being limited to the this and the now – was more apparent than its supposed materiality.
One updating of Berkeley’s argument is that matter (or energy, or whatever should be fundamental in this domain) is not given within the limits of the sensible since it is identified by a sort of eternity and necessity that no object of a nervous system can have. Matter is judged to be always conserved throughout changes and so is extended beyond all actual experience. Matter thus requires some sort of information beyond the this and the now, and so beyond what is fundamentally real to the Empiricist.