Main points
Choice theories, which hold that having a right consists in controlling another person’s duties, appear implausible in some cases, namely, those in which there is little point to being able to waive the corresponding duties.
Raz has a benefit or interest theory (“benefit” and “interest” are synonymous).
It avoids the third party beneficiary and redundancy objections because it holds that interests justify rights and rights justify duties.
Third party beneficiaries do not have rights because their interests are not sufficient to justify the duty in question. Rather, in the case of promises, it is the interest of the promisee in having promises kept that justifies the promissor’s duty, even if the primary beneficiary is a third party.
Here, I finally got back to a point that Kiran and others were making last time: that the promisee has an interest in the performance of a promise, even when there is also a third party beneficiary. Raz handles Danielle's point, that the third party beneficiary (Z) benefits but has no rights, by saying that Z's benefits are not sufficient to justify holding X under a duty to care for Z. So while Z does benefit from X's performing his duty, that fact is not sufficient to justify holding X to be under a duty and so the fact that Z does not have a right does not conflict with Raz's version of the benefit theory.
Rights are not redundant with duties because they justify them. For example, one right could justify different duties in different circumstances; this is what Raz calls the dynamic aspect of rights, namely, their ability to justify different duties in different circumstances. Since that is so, rights are not simply redundant with duties.
Problems
Raz’s theory is that interests justify rights and rights justify duties.
But whether there are duties or not depends on factors that are independent of a person’s interests. My interest in receiving an education is the same whether the people in my society can afford it or not. If they have to chose between education and eating, they might well have no duty to build schools, even though I have a strong interest in receiving an education.
Raz tries to get around this difficulty by distinguishing between general rights, which do not logically entail the existence of corresponding duties, and particular rights, which do entail corresponding duties. But since he also holds that rights are sufficient to justify holding others under duties, it is hard to see how he can call general rights rights. (see Raz, pp. 211-212)
Note: Raz and Hart do not mean the same thing by “general rights.” Sorry.
This raises a broader problem: what do rights do in Raz’s theory? For example, why couldn’t we just replace them with very important interests that can be protected by holding others under duties? If we can make that replacement without losing anything important, then it seems that Raz’s theory does not actually explain what is distinctive about rights, that is, what rights do that other moral concepts do not. (Raz has an answer, but I will leave that to you to find).