The central thesis of this chapter is that Husserl takes over from the classical philosophical tradition the strong foundationalist account of scientific knowledge as a unified system of deductively interconnected necessary truths derived from self-evident universal and generic principles. In response to some of the standard objections to Husserl’s philosophy of science, however, it will be noted that he neither applies this account tout court to the empirical sciences in general nor to the physical sciences in particular.

The term “strong foundationalism” is taken from the literature of contemporary meta-epistemological research within Anglo-American philosophical circles. Most generally, it denotes a conception of the structure and properties a specified body of beliefs must have if it is to count as science, knowledge, or, at least, a body of justified beliefs. The guiding intuition of foundationalist epistemologies is that within a given cognitive structure, a distinction is to be drawn between beliefs that are based upon other beliefs, and beliefs that are not based upon other beliefs but are themselves basic. Some beliefs are founded; others will serve as the foundations. In the context of a theory of justified belief, a foundationalist will hold that while we are justified in holding some beliefs only on the basis of other beliefs, we are justified in holding basic beliefs without further ado. If we were not to recognize some beliefs as properly basic and held that for every belief we would be justified in holding it only on the basis of other beliefs, the process of justification could never be brought to proper closure. For any belief that served as the basis for another belief would in turn be based upon another belief and so on ad infinitum. Any point at which the process of justification was brought to a halt would be, strictly speaking, arbitrary, and no belief would be ultimately justified.

This foundationalist intuition is given clear expression by Husserl himself in the opening sections of the Cartesian Meditations, where he makes a distinction between mediate judgments and immediate judgments in connection with the idea of science. Mediate judgments are grounded on other judgments, whereas immediate judgments are grounded not upon other judgments, but upon the direct intuitive experience of the state of affairs judged (CM, 10 / H I, 51). Likewise, in Ideas I, Husserl speaks of “immediately evident judgments,” to which all other judgments ultimately refer back in the process of “mediate grounding” (ID I, 13 / H III 1, 18; see also ID I, 338 / H III 1, 326).

Strong foundationalism, as opposed to various forms of weak foundationalism, holds that only those beliefs that are certain, evident in the strongest sense, can count as properly basic. In Husserl’s understanding of the structure of scientific knowledge, this requirement of strong foundationalism represents an essential component of the idea of genuine science. For “genuine science and its own genuine freedom from prejudice require at the foundation of all proofs,” as Husserl has it in Ideas I, “immediately valid judgments which derive their validity [directly] from originally presentive intuitions” (ID I, 36 / H III 1, 42). In the introduction to Formal and Transcendental Logic, he asserts that the sciences, if they are to be genuine, must be grounded on a foundation that is “absolute” (FTL, 7 / H XVII, 6). In the First Meditation of the Cartesian Meditations, Husserl insists that the question of the beginning of science, the foundation, is the question of “those cognitions that are first in themselves and can support the whole storied edifice of universal knowledge” (CM, 14 / H I, 54). As such, these cognitions “must carry with them an absolute certainty, if advancing from them and constructing on their basis a science governed by the idea of a definitive system of knowledge … is to be capable of having any sense” (CM, 14 / H I, 55). For what the scientist demands of all principles is “absolute indubitability” (CM, 15 / H I, 55).² As we will see in chapter 2 of this study, it is the specific task and overarching aim of phenomenology, as a transcendental first philosophy, to provide the sciences with a foundation that meets this requirement. Our concern here will be restricted to the strong foundationalist account of science, although there are many instances one could cite of strong foundationalism as, more generally, an account of knowledge or justified belief.

But the formal structure of the strong foundationalist account of science had already been decisively articulated long before by Aristotle in the Posterior Analytics. I will refer to the core content of this early formulation of the conception of the structure of scientific knowledge as the “classical idea of science.” It was destined to become the dominant way of understanding the nature of science and displays a remarkable degree of conceptual tenacity to this day. Ensconced in the Scholastic concept of scientia, it managed to survive the flood of philosophical criticism directed against the Aristotelian-Scholastic tradition by the early modern philosophers, and immediately re-surfaced within the new setting of the Cartesian philosophy of the cogito. Not until 1899, with the “axiomatic turn” accomplished in David Hilbert’s formalism, did the classical idea meet a worthy contender within the circle of the formal disciplines, where it traditionally held sway.

According to Aristotle, a fact may be known, but it is not known scientifically unless and until it has been demonstrated from premises that are more general and better known. When such a demonstration has been carried out, we will know not only that a certain fact is the case, but why it is the case, the conclusion being related to the premises as effect to cause (PA, 71b20–22). But if the premises from which the initial demonstration proceeded are themselves to be known scientifically, they must in turn be demonstrated from other premises that are still more general and better known. Thus, at each level of discursive reasoning, the demand for a demonstration of the premises can be reiterated. But if the process of demonstration is not to become involved in an infinite regress, it must eventually terminate in premises that are themselves “indemonstrable” (72b19–22). These propositions will serve as the “axioms” of the system of demonstrative knowledge that is to be derived from them. They themselves are not demonstrable in terms of propositions that are more basic. Rather, they are grounded in an immediate rational insight (nous) into their truth. Propositions that serve as axioms are not known on the basis of other propositions that provide evidence for them. We hold these truths to be “self-evident.”

What holds for the order of propositions also holds for the order of concepts. Some concepts are defined on the basis of other concepts. The latter concepts can, in turn, be defined by other concepts. But if the process of definition is to come to an end, some concepts must themselves be basic and indefinable. The primitive concepts within a cognitive structure cannot be further defined, but are derived from an immediate rational insight into the generic essences of the object domain under consideration.

According to the Aristotelian conception, then, scientific knowledge is demonstrative knowledge. By virtue of its logical structure, all demonstrative knowledge ultimately rests upon a basis of indemonstrable first principles. If demonstrative knowledge is to count as knowledge, however, the first principles upon which it rests are not to be established on the basis of purely methodological desiderata; nor are they to be hypothetically postulated for subsequent testing. For then they would be uncertain and ultimately no better than mere opinion. Rather, the foundations of genuine science must be absolute. The first principles of a science are to possess the certainty that is achieved through the clear apprehension of the necessity of their truth. The science constructed on those first principles through the systematic derivation of all and only that which is entailed by the first principles will then be certain throughout. For the entire science will be exclusively composed of necessary truths about that which “cannot be otherwise.” And such is Aristotle’s position: “Scientific knowledge and its object differ from opinion and the object of opinion in that scientific knowledge is commensurately universal and proceeds by necessary connections, and that which is necessary cannot be otherwise. So though there are things which are true and real and yet can be otherwise, scientific knowledge clearly does not concern them … it is opinion that is concerned with that which may be true or false, and can be otherwise” (PA, 88b30–89a2).

In sum, the classical idea of science, as initially formulated by Aristotle, can be characterized in the following way: Science is a unified system of necessary truths deductively derived from self-evident first principles. The first principles of any science will be composed of universal principles that necessarily hold for all beings, generic principles that necessarily hold for all beings within the relevant genus, and the first principles of logic, presupposed by all demonstration.

Scientific knowledge, then, according to Husserl, is grounded knowledge. It is achieved through a demonstration in which the fact to be scientifically known is deduced from antecedent conditions. For any state of affairs that we would claim to know scientifically, we must be in a position to show how it necessarily follows from other states of affairs. If, in turn, we are to claim to know these antecedent states of affairs scientifically, we must also be in a position to show how they follow from other states of affairs. The process of grounding knowledge is reiterable (CM, 10 / H I, 51). But it must eventually terminate in certain principles if it is to avoid either an infinite regress or a circularity (LI I, 116 / H XVIII, B 84). Such principles must be immediately known if they are to function as the first principles of science wherein all other propositions of the science are grounded. They themselves are groundless, if by “groundless” we simply mean that their truth is not apprehended on the basis of other propositions (LI I, 152 / H XVIII, B 134). Thus the very idea of science contains within itself the distinction between mediate and immediate judgments. Mediate judgments are ultimately grounded in a deductive fashion in immediate judgments. The immediate judgments are grounded not in other judgments, but in the direct intuitive experience of the states of affairs corresponding to them (CM, 10 / H I, 51).³

Although Husserl admits that the methods of science include much more than deductive thought sequences, he nonetheless holds the latter to be of central significance. All other methods employed in science, he maintains, are either substitutes for such arguments or “auxiliary devices” that “prepare, facilitate, ensure or render possible” subsequent thought sequences by which certain propositions are deductively grounded (LI I, 68 / H XVIII, B 23). Examples of the first class would be certain “algorithmic methods,” “whose peculiar function is to save as much genuine deductive mental work as possible by artificially arranged mechanical operations on sensible signs” (LI I, 69 / H XVIII, B 24). Also included here would be certain procedures by which objectively valid empirical judgments are obtained. Examples of the second class would include the disambiguation of terms, the development of a symbolic vocabulary, and classification. All such methods are pertinent to science only insofar as they ultimately relate to the deductive grounding of propositions, for “each actual advance in science is performed in an act of grounding [Begründung]” (LI I, 69 / H XVIII, B 24; translation modified).

It should be clear from the above that, for Husserl, an isolated bit of knowledge, no matter how evident, does not count as scientific knowledge. To be scientific, it must be incorporated into a unified system of grounds (LI I, 62 / H XVIII, B 14–15). “No truth,” Husserl maintains, “is … isolated in science: it occurs in combination with other truths in theoretical connections bound by relations of ground and consequent” (LI I, 173 / H XVIII, B 162). Any judgment that is to count as scientific must have its place in the order of grounds that pertain to a specific discipline (LI I, 63 / H XVIII, B 15). “The essence of science,” Husserl writes, “involves unity in the whole system of grounded validation: not only isolated pieces of knowledge, but their grounded validations themselves … must achieve systematic unity” (LI I, 62 / H XVIII, B 15). The type of systematic unity that is displayed in the structure of science is the “unity of demonstration” (LI I, 227, 229 / H XVIII, B 231, 233). And what constitutes this unity is the one basic proposition, or homogeneous set of propositions, from which all other propositions belonging to that science can be deduced. What makes science science, then, is a...