If you don't know already, this is a famous phrase from the Star Trek franchise, originally spoken by Spok the Vulcan.
In Star Trek, this is posed as a Vulcan theme versus otherwise a human theme. I'm not sure I agree with this.
It's true that in the West, individual liberties and rights are championed and indeed wars have been fought for them. Perhaps nowhere are these ideas more enshrined than in the USA and France.
But in reality, this is not the case. For example, governments the world over must make budget decisions. A little extra in one pot will help some people at the expense of others. If you don't pour all your budget into health care or crime fighting then we can say that more people will die because of this decision.
We can think of this phrase when there is a very difficult decision to be made. Do we risk the lives of many to save just one? That's the origin of this phrase anyway (saving Spok's life versus the crew of the starship Enterprise).
You sometimes see this when a country's armed forces will launch an operation to rescue a single hostage. The hostage is surrounded by booby traps, armed terrorists and suicide bombs. And yet many governments will mount a mission to save them - risking the lives (no matter how skilled) of a group of special forces all to get one person back.
Maybe it's more about the symbolism of at least trying, sending a message that you hold the moral high ground or that taking your countrymen hostage will never succeed.
Then you have those governments who refuse to negotiate with hostages. Eventually, those hostages may be killed because the ransom is not paid. This is the reverse theory: that the needs of the many outnumber the needs of the few, or the one.
If you want to read more about this, check out the subject of 'utilitarianism' (wiki link) - I think you'll find it quite interesting.
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