These axioms greatly interested Husserl, who, in his Lectures on Ethics and Value Theory, expanded upon the project of formal axiology—whereas Brentano had ultimately confined himself to proposing axioms.

Husserl advances a hypothesis suggesting an analogy between theoretical (or judicative) reason and practical reason. Drawing a parallel between logic and ethics, and between the types of reason associated with these disciplines—namely, judicative and practical reason—he introduces the idea that, alongside logic, in the narrowly defined sense of a formal logic, must also correspond in parallel a formal and also aprioristic practice in an analogous sense ¹.
For Husserl, the realm of praxis encompasses both ethics and evaluation in their broadest forms. This gives rise to the Idea of a formal axiology as a formal aprioristic discipline of values, or of value contents and value meanings - a discipline which, for essential reasons, is intimately intertwined with that of formal praxis ².

To assess whether the analogy between the theoretical and practical spheres is valid, we must determine whether formal ethical and axiological laws can indeed be discovered.

The task, then, is to formalise axiology, which, as D. Pradelle summarises, involves abstracting from any specific or material determination of values, stripping them of content to examine only the bare value-form of value itself ³.

One of Husserl's findings is that the law of excluded middle—either a door is open or closed (A or non-A), with no third option—does not apply in formal axiology. In its place, he introduces the principle of the excluded quarter: something may have a positive value, a negative value, or no value at all. In the axiological domain, there are three fundamental value modalities—positive value, negative value, and null or indifferent value (adiaphoron) ⁴.

Husserl thus proposed several formal axiological laws, drawing in part on Brentano's work—for instance, that a pure good is more valuable than a good mixed with evil. We must, however, return to examining formal axiology as a broader project rather than dwelling on the specific results it has managed to achieve.

1. Lectures on Ethics and Value Theory, Section 1, §1
2. Ibid.
3. Ibid, preface
4. Ibid.