(Part VIII of this series)
If the reader found Locke’s unabashed eye-for-an-eye ethic regarding murderers excessive, what comes next in this chapter is even more bizarre a logical leap:
“This makes it lawful for a man to kill a thief, who has not in the least hurt him, nor declared any design upon his life, any farther than, by the use of force, so to get him in his power, as to take away his money, or what he pleases, from him; because using force, where he has no right, to get me into his power, let his pretence be what it will, I have no reason to suppose, that he, who would take away my liberty, would not, when he had me in his power, take away every thing else.”
— John Locke, Second Treatise on Civil Government, Chapter 3
He at least gives a reason for this view, but it’s one we would unequivocally condemn for its rashness of judgment. Even if Locke refers not to petty theft here, but to serious embezzlements or bank robberies — being generous, since he in fact cites theft of a horse or coat as worth killing over — it seems hardly sensible to infer total hostility and non-negotiability from a willingness to steal property of a non-essential sort (not integral to a person’s well-being, that is). That’s a heavy burden of proof to shoulder when making claims about human nature upon which lives depend. Here we see a simple but important example of a way ethical and legal determinations concern probabilistic facts, given an agreed-upon premise of value.
As backward as Locke has gotten the details, his broader point stands fairly well: Without government, people are in a state of nature in which we may get along cooperatively to some respectable degree, delivering informal justice, and it is when one person threatens the crucial property of another that “war” is declared. Such is a circumstance in which one may suspend the general rules of non-harm for a greater good, although of course it would be wise not to use more force than is necessary for that good.
As the chapter concludes, Locke brings his points together, expressing the necessity of war as a proper response to an aggressor’s attempt to dodge justice. The bottom line in this theorizing about the state of war is that society emerges when people seek to minimize the frequency with which they must resort to war. Ideally, we implement a justice system by which harmful actions are discouraged or prevented by the deterrence, isolation, and/or rehabilitation of would-be dangerous individuals, without using the extreme force of war.
Now we have seen some reason to consider Locke as moderately fallible a thinker and moralist as we should expect any human to be, but delving into more of his treatise should prove fruitful in uncovering the essentials of how rights, laws, and justice work.
Saving the World for Dummies 
It seems from the quote that Locke is talking about being “mugged”. The scenario is one where you are robbed under a threat upon your life, and he seems to be saying that to defend yourself against a threat of deadly force you may use deadly force yourself. In other words, the thief has “declared war” upon you to extort your property (as opposed to the pickpocket who threatens you with no violence and takes your property by stealth).
I would agree with your charitable interpretation if it weren’t for this: “…to kill a thief, who has not in the least hurt him, nor declared any design upon his life, any farther than, by the use of force, so to get him in his power…”
Locke seems to be going out of his way to distinguish this from a violent mugging situation, especially considering he argues for the justice of killing the thief not for self-defense against readily apparent danger, but as a preemptive measure given dubious evidence of risk. It’s not deadly force, but an attempt to subvert the victim’s liberty, that Locke perceives as the direct threat. I’ll criticize the denial of one’s freedom as much as the next person, but the use of deadly force where it isn’t evidently necessary is definitely not something I can get behind.
The way I’m reading the quote is that (a) the thief intends to steal rather than to murder (” a thief, who has not in the least hurt him, nor declared any design upon his life”) but also that (b) the thief is willing to do whatever is necessary in order to accomplish the theft (“to get me into his power, let his pretence be what it will, I have no reason to suppose, that he, who would take away my liberty, would not, when he had me in his power, take away every thing else”).
It’s like a car-jacking at gun-point. If you put up no fight, the guy gets the car. If you resist, then he is willing to shoot you to get the car. The thief has not come to the car to kill you, but he will if necessary.
But you’ve read the context and I haven’t, so I may very well be wrong.
I can see your point of view, and actually there’s nothing about the context that directly contradicts it. Frankly, it’s not the most fruitful exercise to do exegesis of this treatise as if there are strict Locke-ians who would follow Locke’s words to the letter and kill shoplifters because of them. But I think my point stands that it’s erroneous to make the logical leap Locke apparently makes here: that the subversion of liberty on even the scale of theft is evidence of some indiscriminate willingness on the thief’s part to kill for what he/she wants.
To be sure, such an inference makes sense if the subversion of liberty in question is of a highly serious and fundamental nature — someone with no moral qualm about asserting total authority over another person may reasonably be suspected to have no objection to murder when it suits him/her, either. Whether that implies it’s prudent to kill such an individual is a whole other shebang.
This has been very informative. Thanks for the blog!
And a sincere thanks to you for contributing your thoughts. I’ll reply to some of your comments as time permits.