“Is it theft to use someone else’s wi-fi?” No.
“Is it wrong to use someone else’s wi-fi?” Yes.
“Is it theft to use someone else’s bandwidth?” Yes, because when I use your bandwidth I am taking something from you that causes you to no longer have it.
“Is it theft to use someone else’s wi-fi if it results in using someone else’s bandwidth?” Yes.
“Is it theft to use someone else’s wi-fi if it does not result in using someone else’s bandwith?” No.
“Is it wrong to use someone else’s wi-fi if it does not result in using someone else’s bandwith?” Yes.

Theft means taking something away from someone else, so that they no longer have it.

If you make a COPY of something, so that the owner retains the object, it is *NOT* theft. That does not mean it is not *ILLEGAL* but it doesn’t mean any reasonable definition of theft. It is copyright infringement, which is illegal like theft is, but it is not theft.

Take something, original owner no longer has it = Theft
Copy something, original owner still has it = Copyright Infringement.

You say: “You can steal software, songs, and wifi connections”.

I disagree with this. You cannot steal software or songs unless you walk into a store selling software or cds and physically remove the items. If you merely make a copy, it is not theft. It is copyright infringement, and it is illegal (like theft) but it is not, itself, theft.

We have a tendency to group ‘theft’ in with ‘copyright infringement’ because we have a notion of ‘intellectual property’ being on the same level as physical property. But the distinction between the two is very real, so grouping everything under ‘theft’ is misleading at best and just plain false at worst.

Theft and Copyright Infringement are two different things, but they can both be morally wrong, and they can both be (and are) illegal.

Locking down the definitions of these words makes these sorts of conundrums extremely easy.

“Is it theft to steal wi-fi?” No.
“Is it wrong to steal wi-fi?” Yes.
“Is it theft to steal bandwidth?” Yes, because when I steal your bandwidth I am taking something from you that causes you to no longer have it.
“Is it theft to steal wi-fi if it results in stealing bandwidth?” Yes.
“Is it theft to steal wi-fi if it does not result in stealing bandwith?” No.
“Is it wrong to steal wi-fi if it does not result in stealing bandwith?” Yes.

We do not “hold these truths to be self-evident”: for much of this country’s history, there was no law or social norm supporting the notion that “the right to control copies” was something one could possess and defend. The idea arose when it became useful to have specialists in the mechanics of publishing, and society sought some way to make that worth their while. The question is worth re-asking today: do we prefer a society where these “intellectual property” rights are sacrosanct? Or otherwise?