The idea of ideal objects as multiply instantiable entities appears in the Crisis63 and
Phenomenological Psychology64 and the idea that ideal objects are non-spatiotemporal entities appears in Formal and Transcendental Logic.65
63 Edmund Husserl, The Crisis of European Sciences and Transcendental Phenomenology: An Introduction to
Phenomenological Philosophy, trans. David Carr (Evanston, IL: Northwest University Press, 1970), 357.
64 Edmund Husserl, Phenomenological Psychology: Lectures, Summer Semester, 1925 (The Hague: Nijhoff, 1977). For
example, see Edmund Husserl, “The Task and Significance of the Logical Investigations”, trans. J.N. Mohanty, in
Readings on Edmund Husserl’s Logical Investigations, ed. J.N. Mohanty, 198 (The Hague: Nijhoff, 1977):
“Irrespective of whether it is I or someone else who thinks or proves the Pythagorean theorem, the latter itself is a
unique member of the realm of propositions”.
65 Edmund Husserl, Formal and Transcendental Logic, trans. Dorian Cairns (The Hague: Martinus Nijhoff, 1969), §58,
James Burrowes, Husserl’s Arguments against Logical Psychologism and his Conception of Ideal Objects