In order to get at the argument I want to arrive at I am going to contrast it with a pattern exemplified in a statement from Christine Korsgaard. Korsgaard writes in The Sources of Normativity: "Since you cannot act without reasons and your humanity is the source of your reasons, you must value your humanity if you are to act at all". Here Korsgaard brings together the sense of action with humanity by the connecting notion of reasons and then stresses the view that if there is a source of reason then it is right to "value" that source in order to act. The argument is presented by Korsgaard as a "transcendental" one.
The notion that humanity is a "value" requires commitment to a certain conception of humanity in which it represents some kind of self-standing source of normativity even though Korsgaard wishes to stress that what makes it so is its reflective capacity. So, in a sense, this conception of value is one in which the ability to be able to look at our capacity to reflect (hence a self-reflexivity) is the source of value as such. Implicit in this conception is, I think, a view somewhat like that stressed on occasion by Onora O'Neill who sees reason as the ultimate "value" of Kantian philosophy.
Now, if reason and humanity are connected in the sense that the basis of humanity is the ability to be self-reflective and this ability is treated as a "value" then an important question emerges about how this "value" is related to the process of formal universalisation at work in Kantian ethics? If you take the view of Wood then the lack of apparent connection between the process of formal universalisation and the "value" of humanity points to the need for adoption of the "value" at the expense of the process of formal universality. One of the problems with resolving the unearthed conflict in this way is that if we drop the process of formal universality we are moved to a conception of moral philosophy that seems far from Kantian. Further, if the adoption of a value is the key to moral thinking, then, it would seem, this value is simply set in competition with others that other thinkers happen to hold and there is no evident way of deciding the argument between them.
Rather than follow the thought-pattern underlying the citation from Korsgaard I want to propose a different way of relating humanity to rationality, a way that does not presuppose some conception of "value" that is left unarticulated (and, in any case, is not clearly connected to the process of formal universality). Kant's general argument for respect for persons, expressed in my previous posting, distinguishes humanity from "price" indicating that humanity has "dignity" but no "price". This distinction between "dignity" and "price" is based on a sense that humanity is not commensurable with other things. This lack of commensurability is what leads Korsgaard and others to treat it is a "value" though thinking in terms of "value" in fact presents a sense of commensurability (since values can be "maximised" for example).
The sense of humanity as that which has no "price" is related to the notion looked at in the last posting that there are ends that are not "goals" to be realized. Looking back to the justifications Kant gives of the categorical imperative on the one hand, and the formula of humanity on the other, in the Groundwork helps here. The categorical imperative itself (given in the formula of universal law) is arrived at by contrast with hypothetical imperatives as the latter presuppose certain ends that are already assumed to have value. In contrast, the categorical imperative assumes no pre-given value or any specific end other than what can be prescribed by the law itself.
By contrast to the justification of the categorical imperative the argument in favour of the formula of humanity is grounded on a specific notion of universalisation where what is taken is what is "necessarily an end for everyone" (Ak. 4: 428). This end is the sense of rational nature but it was through the process of rationality that we arrived at the categorical imperative in the first place. Hence there can be no "value" in the formula of humanity that was not present in the categorical imperative. Respect, the notion that was highlighted in the last posting, attaches to humanity since it is in the persons of humanity that we see the law exemplified. Persons are what give examples of morality and in giving respect to persons we acknowledge the law they exemplify so such "respect" is part of the process of formal universality and should not be set against it or assumed to involve a "value" that is distinct from it.