The principle of hierarchical causality has left reality in a very precise situation: change exists, it is intelligible, it is real, and it depends at every instant on actualizing principles. Not in a vague or historical way, but actually.

Yet this imposes a consequence that cannot be indefinitely postponed:

A hierarchical series of actualization cannot be constituted solely of what is in potency.

In other words: there must exist a principle that is in act without any admixture of potency.

This is not a hypothesis added from outside. It is what remains once all escape routes are closed.

Why a first principle in potency is impossible

Let us proceed calmly.

In a hierarchical series:

• each element acts insofar as it is actualized by another;
• its power to act is derived, borrowed, conditioned.

If one supposes that all elements of the series are in potency with respect to their acting, then none is in a position to actualize anything.

It is exactly like a sequence of instruments without a musician, or a chain of mirrors without a light source. One can multiply the relays to infinity: without a first act, nothing happens.

Yet something happens. Change is there. Actualization is effective.

Therefore there necessarily exists a principle that does not borrow its act, a principle that acts without being itself actualized by another.

This principle cannot be simply "first in time"

A classic error consists in believing that this reasoning seeks a first chronological event, a "very first change" situated in a distant past. That is not the point.

The sought principle is not first in time, but first in the order of actuality.

Even if the world were eternal—a hypothesis perfectly compatible with this reasoning—there would still need to be, here and now, a principle that:

• actualizes without being actualized,
• causes without being caused,
• gives without receiving.

The dependence is ontological, not historical.

Why this principle must be pure act

If this first principle still possessed any non-actualized potency, then it could change. And if it could change, it would need to be actualized by something else.

But then it would no longer be first.

Therefore:

• the first principle cannot be composed of act and potency;
• it cannot become;
• it cannot receive a new determination.

It must be pure act—that is, be what it is without lack, without becoming, without dependence.

This point is decisive: pure actuality is not a poetic superlative, but a metaphysical necessity.

What pure actuality immediately implies

At this stage, several consequences impose themselves:

1. Immutability — What is pure act cannot change, since a change would presuppose a potency to actualize.

2. Real Simplicity — What is pure act cannot be composed of parts, distinct principles, or assembled elements. All composition would introduce dependence.

3. Absolute Independence — This principle receives nothing. It depends on nothing. It is not conditioned.

4. Plenary Actuality — It does not have act: it is act.

None of this is yet religious. We have spoken neither of revelation, nor of prayer, nor of morality. We have simply followed, without cheating, the demands of reality as it gives itself.

Down to earth: why this principle is unavoidable

Let us return one last time to ordinary experience.

At every instant:

• something acts,
• something becomes,
• something is actualized.

If everything that acts did so by borrowing, then acting would be impossible. Yet it is there, indisputably.

To say "there are only processes" does not suffice. To say "there are only laws" does not suffice. To say "there are only relations" does not suffice.

A process without act is a word. A law without actuality is an abstraction. A relation without real terms is nothing.

There must ultimately be something that is act without reserve, without condition, without becoming.

Where we stand

At this point in the reasoning, one thing is established:

The changing, intelligible, and structured reality presupposes the existence of a principle that is pure act, without potency, without composition, without dependence.

One can refuse to call it "God." One can defer the identification. But one can no longer eliminate it without denying everything established before.

And this principle, precisely because it is pure act, cannot be thought of as one being among others.

It is this last point—often misunderstood, often caricatured—that will now need to be clarified.

And then, there will not be many illusions left to save.