The symmetry argument

Lucretius' symmetry argument (the mirror)

Lucrèce c. 99 BC · c. 55 BCAtoms swerve slightly by chance (the clinamen): this is what makes the will free.

What it claims

The time after our death is not an evil: there is nothing to fear, nothing sad, not even a bad dream. It is calmer than any sleep.

Why

The time before we were born did us no harm, and the time after death is just like it.

The same idea through history

Épicure300 BCEpicurus lays down the basic idea: death is the end of sensation, so it is nothing to us. In the Letter to Menoeceus he does not make the comparison with the time before birth.

In short

"The symmetry argument" is an argument by Lucrèce (On the Nature of Things, III, 830-842 and 972-977) on the question "Should we fear death?" (answer: nothing to fear). Its claim: The time after our death is not an evil: there is nothing to fear, nothing sad, not even a bad dream. It is calmer than any sleep. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 2 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

On the Nature of Things, III, 830-842 and 972-977

Valid with an implicit premise

For an infinite time before our birth, we were not, and it did us no harm. Lucretius asks us to look at that past as a mirror: the time that will follow our death resembles it in every way. If the first does not frighten us, why the second?

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.

Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a world where the time before birth is no evil, where the time after death resembles it, and where nonetheless the latter is an evil: for instance because it deprives us of a life to come, which the past does not do.

Valid with the hidden premise P4 (two identical states have the same value). Almost all objections attack P4 or P3: they say that the future and the past are not alike for us, because only death deprives us of a life we could have had.

Analogy. You are not sad at having missed a concert given before your birth. Lucretius asks: why would you be sad at missing those given after your death? For him it is the same absence seen from the other side.

Objections

Each objection is a conversation: click to see who replies and where the debate stands.

Thomas Nagel 1970 · attacks premise 4

The two times are not alike for us. The time after our death is a time in which we would have lived had we not died: death deprives us of it. The time before birth is not: had we been born much earlier, we would have been someone else. So our birth deprives us of no life.

a defender replies

see the argument

Stephen Rosenbaum ("How to Be Dead and Not Care") defender of the argument · 1986

Rosenbaum answers Nagel: if we say we could not have been born much earlier without being someone else, we must also say we could not have died much later without being someone else. If the time of birth belongs to who we are, so does the time of death. For him the difference Nagel invokes disappears.

Where the debate stands (our summary)Our summary: the discussion is whether the time of birth is essential to a person's identity, as Nagel supposes, and whether the time of death is or not. Both camps have arguments, and the debate is still open.

Derek Parfit (the bias towards the future) 1984 · attacks premise 4

We are not neutral about time: we care about what awaits us differently from what is past. A past pain leaves us more indifferent than a coming one. It is therefore normal to treat the future and the past differently, including what will happen after our death.

Lucrèce replies

We have not yet found a direct reply by Lucrèce in the texts.

Anthony Brueckner and John Martin Fischer 1986

Brueckner and Fischer use this bias to defend the asymmetry. Dying early deprives us of future goods, which we care about; being born late deprives us of past goods, which we do not care about. So it is reasonable to regret one and not the other ("Why Is Death Bad?", 1986).

The debate goes on (our summary) Our summary: Parfit describes this bias and discusses whether it is rational; he does not write an answer to Lucretius in this passage. A defender of Lucretius can say that this bias is exactly what he wants to correct: an asymmetry of our feelings is not an asymmetry of the facts.

Where the debate stands (our summary)Our summary: everyone admits we prefer the future. The question is whether this preference is enough to justify fearing death without fearing the time before birth, or whether it is precisely the bias Lucretius denounces. No widely accepted answer.

What today's voices say

Defend it

Ricky GervaisAnswers 'what is it like after you die?' with 'what was it like the 13.5 billion years before you were born? I think it's like that.'

Neil deGrasse TysonOn death he asks whether you had consciousness before you were born and says he sees no evidence he will have any after he dies.