Don't read this if you have not seen Avengers: Infinity War and/or hate spoilers. Heed this warning because there will be no others... Otherwise, enjoy some pretentious reflections on a bash 'em up blockbuster

When I was still in high school, a religious studies teacher presented a no-win hypothetical to the class. What if, he said, you were travelling on a hijacked bus? The terrorists plan to kill half the passengers but, because they're sadistic, they gave you a gun and ordered you to select and execute the victims.

They warn you that if you don't comply, they will kill every last man, woman and child on the bus - your own self-included.

What would you do in that situation? What should you do in that situation? Would the answers to those questions be the same?

This dilemma can be posed in a number of varieties and flavours.  And perhaps because it is so vexing, it is also something of a staple of popular culture. From Sophie's Choice to the Kobayashi Maru to The Good Place, the idea of being forced into deciding who lives and who dies seems to make for watching pleasure.

If Marvel's Infinity War has anything to say on the question, it appears to come down firmly against the utilitarian and on the side of individual life - even where the consequences are grave.

Thanos, the Big Bad of the Marvel Cinematic Universe, is revealed in Infinity War to be a simple Malthusian worried about the finite nature of resources. Concerned that the spread of life will exceed the universe's ability to provide, he seeks to restore balance by killing half of all living beings. Apparently, the task is quite easily accomplished if you are in possession of six elemental "infinity stones" scattered throughout the galaxy.

As Thanos and his allies hunt the stones down, he hardly revels in his mission. He even expresses sorrow when forced to pay a very personal toll to complete his task. From the start of the film to the end, however, he is possessed of a grim sense of purpose.

If trillions of people must die to safeguard the health and prosperity of trillions then so be it. Thanos is under no illusions that it is a heavy price. But it is one worth paying. For the greater good. The ends justify the means.

The heroes, on the other hand, do not tend to see things this way. At the start of the film, the "Space Stone" is held by Loki, a reformed villain and brother to the hero Thor. When presented with the alternative of seeing his brother killed, he surrenders the stone to Thanos.

The "mind stone" is fused into the forehead of Vision, a sentient android. When he offers to sacrifice himself so it may be extracted quickly and destroyed, the Avengers refuse. They travel to the fictional nation of Wakanda to try to laboriously remove it while improving his life. As Thanos closes in, the others relent and Vision dies while the Mind Stone is destroyed by his girlfriend, the Scarlet Witch.

But the sacrifice is made in vain. Thanos resurrects Vision and then kills him by taking the mind stone. The anguish suffered by the Scarlet Witch was pointless.

Finally, there is the Time Stone, in the possession of a wizard named Dr Strange. At one point in the movie, Strange informs Tony Stark (Iron Man) that he would not think twice about sacrificing him and fellow companion Spider-Man if it means protecting the stone. But, when it comes down to it, he trades the Time Stone to Thanos in exchange for Stark's life.

Why does he do this?

Well, before the battle with Thanos, Strange looks forward in time to assess the outcome of each possible course of action (this being one of his powers, apparently). In the millions of scenarios he examines, there is only one that involves victory over Thanos. He never reveals what it is but, if his actions are any guide, it must involve the survival of Tony Stark.

And this, I think, is probably meant to be the grand point of Avengers: Infinity War. That sentient beings are not goods to be traded. The lives of individuals can matter in surprising ways and so it is a big mistake to treat any particular person's life as disposable.

The big knock on the Marvel Cinematic Universe is that, for all its competence, reliability and dependable humour, they're not particularly memorable. The villains are forgettable and there is no real "theme" linking the universe together.

The DC Extended Universe, the MCU's great rival, is kind of the opposite. Most of its films, from Superman: Man of Steel to Justice League, have inspired annoyed yawns from the critics. And not even the most hardened DC partisan would admit they are as well made.

But they are interesting at least. There is the common thread of an idea to them. Every movie in the DC canon seems to ask "what would we do if gods walked the Earth?"

Avengers: Infinity War appears to be trying to build up to an important question. At multiple times within the movie, the heroes believed they could have stopped Thanos by sacrificing an individual. As a rule, they refused. So is individual life sacred or fungible?

Let's see where Marvel goes with it.