It is hard to disagree with Locke on his State of Nature and State of War concepts. The maxims presented are almost an innate sense and need not be stated. At the time when he wrote his Second Treatise it would seem they were less obvious than they are today, perhaps that is true or maybe not. Because something occurs naturally does not mean it is not subject to human intervention, and this too occurs naturally. The fact slavery is not possible in the State of Nature does not mean it is not possible in human nature, as we all know.
It does seem natural to want to eliminate slavery, especially if one is subject to a master. What I feel Locke glosses over is the very reality of slavery and human nature. Absolute monarchy is, relatively, a reality in some places today. Maybe it is not “natural” in a sense where people are inevitably doomed to spend the rest of their lives as loyal subjects to the absolute authority of the state. However, being born into a system that promotes a monarch with almost unlimited authority can happen. Niccolo Machiavelli understood this when he wrote his il Principe, a realpolitik book for dummies. Even Machiavelli understands human nature can only endure so much oppression. Machiavelli suggests his prince avoid seizure of his subject’s property because “men sooner forget the death of their father than the loss of their patrimony.” He goes further to tell his prince not to rape, murder or steal from his subjects. Here he recognizes this as the natural state of being (State of Nature). He then offers ways to get around the State of Nature: avoiding these things as much as possible, and only executing for pseudolegitimate reasons can ensure a prince great success. I feel Locke has his ideals in mind, but there is much room for a prince to get away with limiting freedoms rather than striving for absolutism.
If Locke is merely countering Hobbs on absolute monarchy, therein lies many problems. If a prince decides to exercise in a limited monarch, then enough leeway is given to him to maintain, to at least some degree, necessary legitimacy to inhibit the State of Nature. What, then, constitutes the State of War? If a ruler can prevent this State of War by exercising cruelty and compassion in a manner that never really constitutes the State of War for the greater population, individuals can suffer indefinitely. Basically, unless a significant population perceives a threat, individuals will always suffer under this black and white example of Nature and War.