One of the war cries of the anarchist Jean-Pierre Proudhon is his famous dictum "Property is theft!"
In a nutshell and very simplified it goes something like this: There was an initial state when there was the world and there was mankind and the entire world was available to be used by every human. THEN property arose and individuals took parts of that property unto themselves and claimed it as their own. In other words, they stole it from the rest of mankind.
For a lengthier discussion, go here.
Then, come back and explain how property is not theft, or else explain why you agree.
It depends on how strict a notion of "property" you have.
If @Unseen had an idea for curing cancer, but that idea required resources from the common property/Earth, then it seems altogether likely that @Unseen taking those resources in order to create a cure for cancer is not theft, but rather a grant of those resources by the (implied or actual) consent of others. Those resources now "belong" to @Unseen for his endeavor on behalf of the common good.
In essence, a large philosophical Kickstarter campaign. Kickstarter can be seen as a metaphor for those willing to allow others to take a portion of the shared resources in order to accomplish some good for the common benefit.
What may then be theft is when someone retains more of the common resources than are necessary, or when one feels entitled to the common resources, or when one's children are entitled to more than the common resources without offering to make a similar valuable contribution.
(as an aside, this is where I think @Simon runs aground, since the evolutionary/biological preference for offspring/family/tribe would seem to run strongly counter to ethics, rather than being supportive of ethics).
Of course, Proudhon's theory is part of the Marxist attack on capitalism. By what right can someone claim to own the means of production and profit by the sweat of others' brows? In other words, by what right can one person claim a large part of what every single contributor of the enterprise has earned for the corporate entity?
So if I spot an empty can in the gutter (worth 10 cents at any recyclers in my state) and take it, I am stealing it from the rest of humanity? Sounds absurd unless we take it as given that all things have an owner, even if they appear to of been discarded, and that owner is every human on the planet.
So, why must we accept that before any notion of property, everything was everyone's property? Why was it not just there and people came/went/used as they pleased.
You're putting words in my mouth. We're talking about how the institution of property began and is justified. And were I a Marxist, I'd concentrate on capital property not personal property.
Bill Gates has coders and engineers and graphic artists and lawyers and factory workers (etc.) who produce his products yet he and other shareholders (many of whom don't work at all for Microsoft) rake in the dough. It's institution of property that allows this.
If property is theft then we need to start correcting the situation by eliminating all borders defining the countries on our globe. This of course would necessitate the elimination of all militaries used to procure said countries. The American Indian would love to know more about Proudhon's assertion.
But Indians were the leading edge of an invasive species. There was a very long time when the Americas was free of the blight of humanity.
"Americas was" seems ungrammatical, but then again N and S American can be viewed as a single land mass with an isthmus in between. A pseudo-plural.
Appropriating something that doesn't belong to you IS theft. The first person to appropriate something unto himself could be said to have stolen it from everyone.
So if I'm a hunter-gatherer, and I do all of the work necessary to hunt a wild boar, including the risk to my own life, the time spent putting together a spear, the time spent in the forest away from my family, etc. ... do I get to keep the boar when I kill it?
Do you really think I have stolen it just by putting in the effort to feed my family?
Do you feel that you are entitled to my boar without making the effort or taking the risk?
Wow. At last, we have found something we agree on.
I doubt if Proudhon considered food to be stolen or a place to set up a tent or hut. The idea of property being toxic arises when people start amassing more than they need to subsist. When they take more land than they need to the detriment of others, when they hoard food or control it in a way that makes it a scarce resource.
Remember, he was arguing against monarchy and the notion that the kingdom was his and everyone and everything in it his chattels.
Proudhon's own words: "If I were asked to answer the following question: What is slavery? and I should answer in one word, It is murder!, my meaning would be understood at once. No extended argument would be required to show that the power to remove a man's mind, will, and personality, is the power of life and death, and that it makes a man a slave. It is murder. Why, then, to this other question: What is property? may I not likewise answer, It is robbery!, without the certainty of being misunderstood; the second proposition being no other than a transformation of the first?"