system
Given the following post, respond as if you're commenting on Reddit:
human
Is a key that cannot unlock anything still a key?

I have an presentation to do in school on this question. My own thoughts are that when the key loses its ability to unlock things, it's no longer a key. My teacher said that it would be good if I could talk a little in the terms of how we can know it's a key at all etc. Would appreciate some help and thoughts from you redditors. (I apologize for my bad english, I hope you can deal with grammar errors.)

I'm not really out for answers on the question, I would greatly appreciate any philosophical theories on this subject though.
gpt
There are prima facie reasons to think keys without proper locks are still keys, and these reasons come from way 'key' is used in ordinary language. (These things might turn out not to be *real* keys, but that conclusion has to come from somewhere else.) Firstly, think of a key for which no lock has been made. A lock could still be made which that key would open. Secondly, think of a key whose lock has been lost - maybe the key was buried in a drawer for decades whilst the door was replaced. These keys don't have locks and we still call them keys. 

One simple way to define keys is by their functional roles - keys are what they are in virtue of what they do, namely open locks. If natural language has any weight, then the above shows that this is simplified, if not wrong, since we call things 'keys' even when they don't open locks. Perhaps, then, keys have to have the capacity to open locks, or have once been able to open some lock. Again that looks simplified or partial (couldn't any object open a lock provided we design the lock to suit that object's shape?).

Your theory suggests things gain and lose key-ness: a things becomes a key when its lock is made, and is no longer a key when its lock is destroyed. This is clearly at odds with common sense, and we typically don't talk about keys in that way. It also suggests that the following situation could occur: you find a key-shaped object and genuinely don't know whether it is really a key or not. We are all key-skeptics until that object is used in the proper lock. That seems weird, and to make that argument you have to claim that we don't know what we're talking about when we talk about keys. That sort of thing generally strikes me as suspicious.