Taxation, by its nature, is not necessarily theft. Likewise, taking something and not giving something in return is not necessarily theft, either. The circumstances are what matter.
By way of example: two men meet on the street. One is selling apples. The other man has money. They agree to an exchange: one man gets $5, the other gets a bushel of apples. The two go on their merry way, happy as can be. No theft here.
A similar circumstance: two men meet on the street. One is selling apples. The other man has money. While the apple seller is distracted, the other man takes an apple and leaves no money. Now, a theft has occurred.
What is the difference between the two stories above? In the first, there is consent between the two parties. In the second, there is no consent. Consent is what makes an action theft or voluntary. There would be no argument whatsoever on this point. So, the question becomes, can one never consent to taxation? Is taxation inherently non-consensual?
The answer to that question is “no.” Taxation is not inherently non-consensual. It can be agreed upon; it can be consented to. Let’s say a group of people get together and decide to pool their resources for some public good (let’s say, common defense). Depending on the structure of their arrangement, they all agree to provide some annual contribution to this goal. This is, in essence, taxation. Furthermore, it is consensual taxation.
But if taxation can be consensual, doesn’t the use of (or threat of) force for compliance necessarily mean that taxation isn’t consensual? Isn’t that evidence against my thesis? Again, not necessarily. Yes, the thief may use force to get what he wants, but even consensual agreements may carry a threat of force. Contracts contain provisions in case one person reneges on his deal. These are voluntary agreements that contain elements of force if certain conditions are not upheld. So, the existence of force is not in and of itself a sign that the agreement is involuntary.
The real question, the one we should be discussing and thinking on, is “what constitutes consent?” If governments “derive their just powers from the consent of the governed,” what constitutes consent? At what point does government “become destructive to these ends”?* Yes, this is the interesting question and one I will not be discussing in this post.
*A quick aside on this point: using the same logic as above, it can be shown that merely being in a minority, losing an election, or not having things go your way in politics is not necessarily a sign of oppression or malfunctioning government.