“Husserl’s work include lengthy treatment of universals, categories, meanings, numbers, manifolds, etc. from an ontological perspective. Here, however, we shall concentrate almost exclusively on the Logical Investigations, which contain in a clear form the ontological ideas which provided the terminological and theoretical basis both for much of the detailed phenomenological description and for many of the metaphysical theses presented in Husserl’s later works.
The ontology of the Logical Investigations is of interest first of all because of its clear conception of a formal discipline of ontology analogous to formal logic. (Here Husserl’s thinking parallels Meinong’s development of ontology as a general ‘theory of objects.). Formal disciplines are set apart from ‘regional’ or ‘material’ disciplines in that they apply to all domains of objects whatsoever, so that they are independent of the peculiarities of any given field of knowledge.
Logic, as Husserl sees it, is concerned in the first place with meanings (propositions, concepts) and with associated meaning-instantiating acts. Most importantly, it is concerned with that sort of deductively closed collection of meanings which constitutes a scientific theory. For Husserl, as for Bolzano, logic is a theory of science. Only where we have an appropriate unity and organization also on the side of the objects (states of affairs, properties) to which the relevant acts refer, however, will we have a scientific theory, so that the unity which is characteristic of the latter must involve both (1) an interconnection of truths (or of propositional meanings in general), and (2) an interconnection of the things to which these truths (and the associated cognitive acts) are directed.
Where formal logic relates in the first place to meaning categories such as proposition, concept, subject and predicate, its sister discipline of formal ontology relates to object categories such as object and property, relation and relatum, manifold, part, whole, state of affairs, existence and so on. Logic in a broader sense therefore seeks to delimit the concepts which belong to the idea of a unity of theory in relation to both meanings and objects, and the truths of logic are all the necessary truths relating to those categories of constituents, on the side of both meanings and objects, from out of which science as such is necessarily constituted (including what we might think of as bridge-categories such as identity and truth which span the division between meanings and objects).
Husserl’s conception of the science of logic is not an arbitrary one.
For formal-ontological concepts are like the concepts of formal logic in forming complex structures in non-arbitrary, law-governed (“recursive”) ways. And because they are independent of any peculiar material of knowledge, we are able to grasp the properties of the given structures in such a way as to establish in one go the properties of all formally similar structures.”
From: Barry Smith Barry & David Woodruff Smith, The Cambridge Companion to Husserl, Cambridge: Cambridge University Press 1995. pp. 27-29.