 Natorp likens this problematic relation of first-order phenomenality and second-order objectivity to solving for X in an equation (Natorp 1887: 258, 262). If the solution(-set) of X is the object for which thinking is to solve, then the sensible appearance is analogous to the notational cipher, “X”, itself, since what-has-not-yet-been-experienced is simply what-has-not-yet-been-constructed. Moreover, just as in solving an equation one can only determine the X in light of other known quantities assumed in the equation, one must in the same way establish the determinations of the problematic object in light of other objectivities (laws) that are assumed (ge-setzt). No such objectivities are ever granted absolutely, of course, but only relatively, namely with respect to the particular problem. They, too, are always susceptible to becoming problems in their turn. Therefore no complete solution—no total determination of the object—can be achieved for any X, except asymptotically. While the fully determinate object itself thus remains a forever unreachable focus imaginarius (see  Section 3),  it is, by the same token, always at least partially determined. And it is this partially determined objectivity as itself a (non-sensible) object of thinking that Natorp considers the second-order phenomenon, even though he will usually just call it a “phenomenon”, simpliciter. This scientific phenomenon, as an objectivity that is progressively constituted by a dialectic between hypothesis and calculation, entirely loses any sense of “appearance”. This reconception of the phenomenon of mathematical physics finds an analogue in geometry’s replacement of constructions “in intuition” by purely logical deductions from Grundlagen (or “functions” in the sense of “hypothetical act”) as epitomized by Hilbert’s Grundlagen der Geometrie (cf. Friedman 1992, Chapter 1; Hilbert 1999), a book cited with approval by Natorp (1910c: 4) and Cassirer (2000: 99, f.). 