Four clarifications fix what the witness establishes, and what it does not. The third carries the objection that presses hardest on the witness.

*First.* The witness is positive: change is actual, and what is actual is possible, Cartesian-certain by the performative catch of [§2.2.1](<2.2.1 Change Is Actual.md>). What follows from it alone is therefore ◇C, and no necessity whatever. The necessity of the Conditions enters only once that possibility is lifted to □◇C by the Necessary Possibility Theorem ([§2.1.10](<2.1.10 Necessary Possibility.md>)) and carried through the Structural Requirement ([§2.4](<2.4 Structural Requirement.md>)), and what is necessary at that point is the Conditions, not any specific configuration. That change is actual does not entail that any particular change must occur in any particular way, or that any specific medium takes any specific form. The necessity of the structure is the necessity of the Conditions; the contingency of specific configurations within those roles is preserved. The Modal Identity ([§2.6.6](<2.6.6 Modal Identity.md>)) and the type/token distinction ([§6.6](<6.6 Life.md>)) elaborate this distinction.

*Second.* The witness does not establish that the ground of experience is mind-independent physical reality. The level-invariance argument ([§2.2.2](<2.2.2 Actuality's Reach.md>)) establishes that whatever the ground is (physical or transcendental) it instantiates T, S, and Φ. The argument's conclusion therefore does not depend on resolving the realism/idealism dispute. What it depends on is the structural fact that any possible ground of any possible experience must instantiate the Conditions, which is established by level-invariance without prejudging the nature of that ground. The consequence for any candidate ground defined by the negation of T, S, and Φ follows on either reading, as established at [§2.7](<2.7 Nothing to Consider.md>): it is not the ground of experience on any metaphysical picture, because no such ground can lack the Conditions it must instantiate to be a ground at all.

*Third.* The witness holds at the ontological level, not merely the epistemic level. This is the contested clarification, and it is answered in stages: the challenge as Stroud and Kant press it, weak Kantianism with its eliminative and agnostic divisions, strong Kantianism, the post-Kantian phenomenological version, and the performative catch that meets them all. (Stroud, Barry, 1968) articulates the sharpest version of the challenge: for any enabling condition P required for experience X, we can only conclude that we must believe P is true, not that P is actually true. The Kantian version is deeper: could the structural Conditions be necessary features of any possible experience without being features of mind-independent reality?

The Kantian response takes two forms that must be separated. *Weak Kantianism* holds only that T, S, Φ are conditions of experience, and that we cannot know whether they apply to things-in-themselves. Langton's *Kantian Humility* -(Langton, Rae, 1998) is the most sophisticated recent version: we can know the relational-structural features of noumena but not their intrinsic properties. Langton concedes the relational-structural features at the noumenal level (Temporality as relational-structural priority, Spatiality as relational distinctness) which gets two of the three Conditions in place at the noumenal level. The Φ dimension is the one where Langton's intrinsic-property humility could apply: persistence-being might be read as intrinsic rather than relational-structural. The present argument does not lean on Langton's concession to deliver Φ at the noumenal level. Φ is delivered by level-invariance ([§2.2.2](<2.2.2 Actuality's Reach.md>)) and by the constitutive line of [§1.4](<1.4 Three Conditions.md>), which derives Φ from what *exchange* requires. Level-invariance delivers the thinner Φ-role because any grounding relation requires a real fact or realizer in which the dependence obtains. That is a bearing claim about the grounding relation, not yet persistence across a temporal interval or an intrinsic-property claim about the ground. Langton supplies T and S at the noumenal level; the argument supplies Φ independently. On this point the strongest recent version of Kantian humility concedes most of what is needed, and is not an opponent.

Weak Kantianism divides further. *Eliminative weak Kantianism* (the view that noumena lack T, S, Φ, or that no fact of the matter obtains) faces a forced choice: a thing-in-itself lacking the three roles at any resolution — nothing ordered, nothing distinguished, nothing borne — is ontologically indistinguishable from nothing, and the ∅ analysis of [§2.7](<2.7 Nothing to Consider.md>) applies to it directly; so it must either collapse into Strong Kantianism or concede that anything with genuine ontological content instantiates the Conditions. *Agnostic weak Kantianism* (the view that we suspend judgment about whether T, S, Φ apply to noumena) is a different matter. It is consistent with the argument's conclusion rather than opposed to it. The argument's positive claim is that T, S, Φ are instantiated at every ontological level, established by level-invariance ([§2.2.2](<2.2.2 Actuality's Reach.md>)). Agnosticism about noumenal T/S/Φ does not deny this; it declines to assert it. The argument does not need to defeat agnosticism; it needs only that agnosticism is consistent with the positive conclusion established independently. If the agnostic pushes further and denies that T, S, Φ apply at the noumenal level, they have ceased being agnostic and become eliminative, at which point the prior clause applies.

*Strong Kantianism* avoids this collapse by holding that the Conditions are features of mind only. It faces the level-invariance argument of [§2.2.2](<2.2.2 Actuality's Reach.md>) directly. A mind that contributes causally structured succession, relational extension, and causal connectivity to experience must itself possess an internal architecture adequate to generate each. The transcendental subject (Kant's term for the unified *I think* that makes experience possible by contributing its form, rather than being an object within experience) cannot provide the Conditions without instantiating them, because contributing form is itself an act with the constitutive requirements the argument identifies. Relocating the Conditions to the transcendental subject therefore does not remove them from the ontological inventory; it confirms them at a different level. The strong Kantian who pushes further (positing a thing-in-itself with no structural character at all) has not identified a domain beyond the argument's reach but has posited nothing at all. The argument of [§2.7](<2.7 Nothing to Consider.md>) applies with full force.

*The phenomenological version.* The post-Kantian tradition presses the same move at higher resolution. Husserl's transcendental phenomenology *Logical Investigations*, -(Husserl, Edmund, 1900–01); *Ideas I*, -(Husserl, Edmund, 1913) recasts the conditions of experience as conditions of the constituting consciousness: the world as it is for-a-subject is shaped by the intentional acts that consciousness performs. Heidegger *Being and Time*, -(Heidegger, M., (1927) 1962) and Merleau-Ponty *Phenomenology of Perception*, -(Merleau-Ponty, Maurice, 1945) develop the program along existential and embodied lines respectively. The reply is structurally identical to the reply to Strong Kantianism: phenomenological constitution is itself a temporal sequence (T) requiring distinguishable acts (S) sustained by a constituting ego (Φ). Husserl's own genetic phenomenology (passive synthesis, time-consciousness in the *Lectures on the Phenomenology of Internal Time-Consciousness*) effectively rediscovers the Conditions inside consciousness, which is what the argument requires at the relevant level rather than what it denies. The phenomenological reduction does not escape the Conditions; it locates them inside what it reduces to.

*The performative catch.* Both Kantian forms also face the catch of [§2.2.1](<2.2.1 Change Is Actual.md>). The act of distinguishing what thought requires from what reality requires is itself a propositional act that instantiates T, S, and Φ at the ontological level, as preconditions of the very act of assertion, not merely as features of the thought's content. The wedge cannot be driven without the driving instantiating what the wedge was meant to separate. A heuristic lexical illustration supplements the closure. In the everyday register, the word *possible* often carries temporal grain: to say X is possible is, ordinarily, to distinguish what is actual from what could become actual, which carries a before/after structure at the level of the concept. This is a feature of common usage rather than a deductive move; a mathematical platonist reading *possibly true* for timeless propositions does not parse it temporally. The load-bearing closure against Strong Kantianism is the level-invariance reply above: any contributing transcendental subject must itself instantiate T, S, and Φ to do the contributing. The lexical observation is supplementary: it shows how ordinary modal vocabulary already presupposes the temporal grain that Strong Kantianism wants to confine to mind, but it does not carry the deductive weight.

*What the third clarification establishes.* Kant sought to save the thing-in-itself by making the Conditions features of minds. The effect of that move is to make the Conditions necessary, which is what the argument requires. Whatever ontological architecture the critic's act of distinction occupies, the Conditions are present within it as the preconditions of that act. The epistemic/ontological gap is not available as a retreat because closing the gap is not a further claim the argument makes; it is what any act of distinguishing them already demonstrates.

*Fourth.* The scope of the witness extends to whatever ontological level hosts the act of cognition itself, and so is not confined to the domain of physical experience. Actual change, witnessing the possibility of change, holds at every level where a denial could be attempted — which is the level the Necessary Possibility Theorem needs it at.


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← [2.2.2 Actuality's Reach](<2.2.2 Actuality's Reach.md>) | [2.3 Necessary Possibility of Change](<2.3 Necessary Possibility of Change.md>) →
