Does the Future Already Exist?

On Physics, Philosophy, Grim Reapers, and God

If you’ve spent any time exploring philosophy or theology debates, you’ve almost certainly encountered the Kalam Cosmological Argument, even if not by that name. It usually arrives as a snappy, three-line punch:

1. Whatever begins to exist has a cause.

2. The universe began to exist.

3. Therefore, the universe has a cause.

It’s catchy and intuitive but this classic formulation of the argument assumes a literal “flow” of time, a sharp moment when reality simply “popped” into being out of nowhere. To survive contact with every interpretation of modern physics and advanced metaphysics, however, the argument needs a bit of an upgrade. Instead of relying on the bumper-sticker slogan “everything that begins has a cause”, the latest version of the Kalam shifts its focus to a deeper, more rigorous mystery: the explanatory pressure of boundaries.

Here is how the modern Kalam works, step-by-step, incorporating interpretations of the true nature of time, the limits of physics, and the bizarre paradoxes of infinity.

Reframing Time: The River vs. The Block

To understand the modern Kalam, we must first address how we think about time.

The classic Kalam assumes what philosophers call the A-Theory of time. On A-Theory, time is like a flowing river. There is an objectively real “now”. The past is gone, the present is real, and the future doesn’t exist yet. Under this view, it makes perfectly intuitive sense to say the universe literally “came into being” from nothing.

But interpretations of modern physics can throw a bit of a wrench into this intuitive picture. While quantum mechanics still treats time much like a ticking clock, Einstein’s theories of relativity are more consistent with a B-Theory of time (often called the Block Universe). On B-Theory, there is no privileged “now”, and time does not flow. All times – past, present, and future – are equally real and exist simultaneously as a static, four-dimensional spacetime manifold. Think of the B-Theory universe like a movie on a DVD. The movie doesn’t “come into existence” scene by scene; the whole disc just exists. The Big Bang isn’t a moment when the universe “popped” into being; it is simply the front physical edge of the 4D block.

Today, physicists and philosophers hotly debate which theory of time is actually true.

The genius of the modern Kalam is that it doesn’t care who wins the debate. It works on dual tracks. If A-Theory is true, the universe dynamically burst into existence, obviously requiring a cause. But if the B-Theory is true and the universe is a static 4D block, we need to ask structural questions about it. Does this reality extend infinitely in the “past” direction, or does it have a finite edge? If reality has a boundary, we are entirely justified in asking: Why does this specific, bounded universe exist rather than absolutely nothing?

Phase 1: The Explanatory Principle

The first step of the argument establishes that finite, bounded structures are not self-explanatory. If A-theory is true, the principle is obvious: things don’t pop into existence uncaused. But sceptics often look at the B-Theory Block Universe and say, “It’s a static block. It doesn’t need a cause because it never dynamically happened”.

The Kalam defender points out a massive logical flaw here: being static does not make something self-explanatory. If you found a giant, luminous sphere in your garden, you wouldn’t say, “It doesn’t need an explanation because it isn’t moving”. A structured, finite object demands an explanation for why it exists. Bounded, contingent structures cannot be brute facts.

And what about quantum mechanics? Sceptics often claim that “quantum particles pop into existence from nothing”. But the “quantum vacuum” of modern physics is not nothing. It is a physically real state: a highly structured sea of fluctuating fields governed by precise mathematical laws. The modern Kalam doesn’t ask what triggered a specific quantum fluctuation; it asks what explains the existence of that entire underlying framework.

Phase 2: The Pincer Movement (Does the past have a boundary?)

Phase two is where the modern Kalam argues that the universe is not eternal. It executes a “pincer movement” using both modern science and the logical absurdity of infinite causes to prove spacetime has a beginning (or a front edge).

The Scientific Arm: The BGV Theorem

Modern astrophysics relies heavily on the Borde–Guth–Vilenkin (BGV) theorem. In simple terms, this theorem shows that any spacetime that is, on average, expanding cannot stretch backwards into the past forever. This places a hard mathematical limit on past-eternal models. Even complex multiverse theories hit a boundary. Physics keeps nudging us toward a finite limit.

The Metaphysical Arm: Causal Finitism and the Grim Reaper

When sceptics defend an eternal universe, they often point out that mathematics handles infinity just fine. But translating an infinite chain of causes into concrete, physical reality creates ontological chaos. Modern Kalam defenders illustrate this using a thought experiment known as the Grim Reaper Paradox.

Imagine you are alive at exactly 12:00 PM (noon). Now, imagine there are an infinite number of Grim Reapers who want you dead. They operate under a very strict rule: a Reaper will only strike if you are still alive when their appointed time arrives.

• Reaper 1 is scheduled to check on you at 1:00 PM.

• Reaper 2 checks at 12:30 PM.

• Reaper 3 checks at 12:15 PM.

• Reaper 4 at 12:07 PM… and this division goes on infinitely, getting closer and closer to 12:00 PM.

Here is the reality-breaking paradox: You will definitely be dead by 1:00 PM. But which Reaper killed you? It is logically impossible to answer. It couldn’t be Reaper 1, because Reaper 2 would have killed you first. It couldn’t be Reaper 2, because Reaper 3 was scheduled before him. For any specific Reaper you point to, there is an infinite number of Reapers who would have already done the job. No single Reaper can ever swing his scythe, yet you end up dead. The scenario generates a causal black hole: an event occurs, but the chain of cause-and-effect is completely paralysed.

What this means for the Kalam: The Grim Reaper perfectly illustrates the fatal flaw of an infinite past. If “today” is the destination, and the past is an infinite series of prior causes that had to happen before today could arrive, today could never happen. You would be endlessly waiting on a prior event in a frozen causal chain. Because “today” has arrived, the chain of past causes cannot be an actual infinity. The universe must have a finite boundary.

Phase 3: The Transcendent Ground

If the pincer movement succeeds, we are left with a spacetime reality that has a past boundary. So, what explains it? Because the universe contains all of space, time, matter, physical laws, and the quantum vacuum itself, the explanation cannot be found inside the universe. You cannot use a piece of the universe to explain the whole universe.

Therefore, the ground of reality must be:

• Non-spatiotemporal (outside of space and time)

• Immaterial (not made of physical matter)

• Extraordinarily powerful (capable of actualising physical reality)

At this point, we have officially left purely physical naturalism behind.

Phase 4: The Mind at the Edge of Time

How do we get from a timeless, spaceless “ground of reality” to a personal agent? This phase solves the ultimate puzzle: the timeless-to-temporal transition. Imagine the cause of the universe is just an impersonal, timeless force. In everyday life, mechanical causes don’t wait. If a fire is burning, the heat is present. If an impersonal cause exists eternally and timelessly, its effect (the universe) should also exist eternally and timelessly. A mindless equation cannot “choose” to make a universe that is exactly 13.8 billion years deep. But we’ve already established that the universe is not eternal; it has a finite boundary. How can a timeless cause produce a temporally bounded effect (like a dynamic first moment or a finite 4D block)? The modern Kalam argues there is only one known explanatory model that bridges this gap: Agent Causation. A mind with free will can possess the power to create but freely choose when and how to exercise it. The asymmetry isn’t caused by a mechanical gear turning in a timeless void; it is caused by an intentional act of a transcendent Mind that decided exactly where to draw the boundary.

The Final Verdict

This modern formulation (the “New Kalam Cosmological Argument”) is a formidable intellectual structure. It forces a stark choice upon the sceptic: either to accept that our massive, highly structured universe exists for absolutely no reason at all (a Brute Fact), or to follow the explanatory breadcrumbs of our bounded reality emerging from a timeless void to an intentional transcendent mind.

Author’s Note : If the Block Universe is true, can I have free will?

If you made it through the section on the B-Theory Block Universe, your brain is probably spinning. If the future “already exists” as a static location on the spacetime timeline, does that mean our lives are pre-written? Are we just puppets acting out a script?

The short answer is: No, you can still have free will.

When we say that “the future already exists”, our language traps us. The future hasn’t already happened (which implies it’s in the past). Rather, the future equally exists. Think of a map: just because London and Tokyo exist at the same time as your current location doesn’t mean your current location is an illusion. Time works the same way. The year 2050 is just a location over there on the timeline.

Going back to the DVD analogy: a person in a documentary makes a choice in Scene 5, and that choice causes the outcome in Scene 6. The fact that you, holding the DVD, can see that Scene 6 is physically printed on the disc doesn’t mean the person’s choice was an illusion. Their choice is the reason Scene 6 looks the way it does. In the Block Universe, your choices still author your future. It is just that your choices, and the outcomes of those choices, are eternally painted onto the 4D canvas.