If you design and sell a product without patenting it, and I copy the design and sell a competing product, have I stolen from you?

The only difference between the two scenarios is that one involves copyright infringement. Theft means a possession was taken. Potential income is not a possession. There are various ways to describe the harm ("damages" comes to mind) but "theft" isn't among them.

Well if you did patent it, it's stolen. The equivalent for books is copyright laws, so if the work is protected copyright then yes, you've stolen.

And theft is defined as stealing, which has "to take or appropriate without right or leave and with intent to keep or make use of wrongfully" which applies fully here so...

You can nit pick definitions all day, but you'll find most people would consider this theft, as you're depriving the artist of the rights to their creation. I really feel people who want to argue the other way are a stain on this earth, because you're so happy to defend it...it's just mental gymnastics to a pathetic argument

Patents in their current incarnation are theft.

Lemme give an example of how I see this:

I have some idea to do something in a certain way, and because of that I declare it forbidden to everyone else to do it the same way, except they pay me something to be allowed to do it that way.

Wouldn't you think of something like F! How dare he/she/it/whatever?

I don't mean to nit pick, but it's seems like the only way to iron this out. "Theft is defined as stealing" isn't right. Rather: theft is defined as stealing property (or services). Property means real possessions in this context, not intangibles like IP.

A person can steal an idea (or market share) and it wouldn't make them a thief.

The fact that a victim of copyright infringement may end up disadvantaged to the exact same extent as if they were a victim of theft does not magically equate the two, even if the two involve stealing.

It is almost as if the efforts by the RIAA et al ( framing copying as stealing, would you steal a car? ) have worked.

My comment is in the red.

> Theft means a possession was taken.

Usually, but not always, which is why theft of electricity is a thing.

Unlike ideas and other intangibles that are subject to trivial copying, electricity falls into the realm of the physical world. Also, theft of services is an established type of theft along with theft of property.

What's being stolen in theft of electricity? The electrons or the holes?

Service. This question "is a copy equivalent and trivial to create?" is a pretty good way to understand the line in the sand regarding what stuff is subject to copyright infringement versus theft. We have theft of property and theft of service. We do not have theft of trivially copyable stuff because we have copyright infringement instead for that case.

Paintings, manuscripts, etc. are subject to theft because they are nonfungible. The content itself is subject to copyright because the copies are fungible.