I'd be lying, if I said I wouldn't take satisfaction in eliminating the narcissistic/sociopathic/psychopathic from the World, but I take no pleasure in killing (especially not plants or animals).

But, when you've done your best to resolve matters as humanely ¹ as possible (as you have by sealing your home ² ), any steps you take after that aren't evil as such.

When you get ill and take antibiotics, you don't feel guilt or remorse afterwards, for killing the bacteria.

The mouse is no different, just bigger and furrier.

You too have a right to life and health as much as any mouse.

Sadly, the humane (there's that word again) traps don't work — the mice just come back again, finding their way back to their den by smell.

Glue traps are (ironically) inhumane.

So that just leaves snap-traps, I'm afraid.

But, if you put their bodies out in the garden, something will make a meal of them, or they’ll become wormfood and the cycle of Life continues as it should — it's only humans that try to unnaturally preserve our remains ³.

The needless use of plastic, yeah, that's an evil. It stems from Consumerism: typically, Feminism was subverted and, instead of freeing women condemned us all instead to a life in which a single income isn't sufficient to keep a roof over one's head any more and thus it's no longer possible for one person to go to a place of employment whilst their partner goes grocery shopping and buys. fresh, just what is needed for that day each and every day — but it was naive to assume that class warfare would be abandoned by the plutocrats simply because women became nominally emancipated, wasn't it?

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¹ It's funny, isn't it? But as soon as you hear the word humane (more so humanely), you just know something's gonna die.

² I imagine the seals weren't very happy about that though — a very humane approach indeed on your part.

³ Well, the traditional Tibetan take on the process is a more natural approach: when you die, you are left out for the birds and animals and, once they've had their fill, whatever few bones are left are put under a pile of rocks — I'd want to be seen off in the same way but it's just no practical in a metropolis of millions, unfortunately.