The rationalism and metaphysics of the modern period
It is with Hume that sensualism first comes to a fully conscious and universal unfolding. Berkeley had been a sensualist only in his interpretation of the intuitions of external nature. Things are complexes of sensory data that are given in the immanence of consciousness itself. Transcendent material things are fictions; there are no material substances. But sensory perceptions, according to Berkeley, presuppose the perceiving subject, the Ego; for Berkeley the Ego is not a mere designation for some collection of merely associatively related psychic experiences. Rather, sensory perceptions taken as a whole, but also all the other subjective occurrences, all the acts and states of the Ego taken together, have in the Ego as mental substance a principle of unity.
Husserl Edmund (2019) First philosophy: lectures 1923/24 and related texts from the manuscripts (1920-1925). Dordrecht, Springer.
Husserl Edmund (2019) The rationalism and metaphysics of the modern period, In: First philosophy, Dordrecht, Springer, 188–205.