Faith is a loaded word, … . So we are being more precise (and less confusing) if we replace the term faith with "unverified belief." So let's do that.
Certainly we can substitute 'unverified belief' for the word 'faith'. That highlights that we are talking about belief, and as such, I feel the need to set out some preliminaries of my own. To my mind, James is blurring the distinction between our collective knowledge about the world around us and an individuals self-perceived emotional and psychological needs.
In my view, knowledge is defined as reasoned expectation based on experience. What we know of the world around us is through our experience of it, and importantly for human beings, the communicated experiences of others. These cumulative experiences allow us to develop a growing understanding of the world that allows us to make assumptions, predictions, assess odds of likely outcomes, and inform our beliefs. The greater our experience of or with a phenomenon, the more information we potentially have upon which to draw conclusions, which gives rise to greater understand, or knowledge. Essentially, since knowledge is gained through experience, and our experience can have limitations, the knowledge that we hold is held with some level or degree of confidence.
Belief I would simply define as an individual's subjective opinion about anything, be the matter objective in nature or purely subjective, and these beliefs can be influenced by more than objective evidence of the world. We are flawed and fallible creatures (and emotional, as James concedes) and for many reasons we can hold beliefs that are partially to completely inaccurate or false. We can draw incorrect conclusions from too little information, our perception of the matter at hand may be flawed. We can be instilled with specific beliefs through socialization, indoctrination, or coercion, regardless of whether the beliefs have adequate evidential support or reflect reality.
If the subject of the discussion is about objective reality, whether something is real and existent, then, in such a discussion we should disregard the consideration of individual beliefs altogether. James titled his lecture “The Will To Believe” and we know from experience that we all, even the brightest among us, can hold beliefs that are not true. We know that beliefs are malleable and can be influenced and shaped by many factors, some of which I listed above. It is this will to believe, this emotional need and desire to believe, that gets us into trouble. Let's look at the Wikipedia definition for confirmation bias:
Confirmation bias is the tendency to search for, interpret, favor, and recall information in a way that confirms or supports one's prior beliefs or values. …
The effect is strongest for desired outcomes, for emotionally charged issues, and for deeply entrenched beliefs.
Confirmation bias - Wikipedia
When it comes to religious belief, I think it is fair to apply the characterization of emotionally charged and deeply entrenched. James has built his rationalization for a belief in God on belief, and for that primary reason, his argument falls short.
If we must disregard belief, that means we are left with our knowledge gained through experience, in essence empiricism. From what I can gather from the Wikipedia abstract on “The Will to Believe”, James supports and is an advocate for empiricism, over what he seems characterizes as dogmatic absolutism. As I tried to convey in my previous post referencing the mountaineer hypothetical, I do not believe any of James's hypotheticals really represent unverified belief, but rather, all of them are grounded in, and informed by, experience. Certainly the outcome is not guaranteed, but the choice to act or the hoped for or expected outcome are all informed by experience. If one has insufficient information or experience and feels compelled to choose, then we characterize that as a guess, or a hope, not a true belief that is unverified.
Contrast this now with a belief in an entity or entities that we are unable to observe or directly experience (in a verifiable way) that exists in a realm that is undetectable by any means. If we believe in such entities and undetectable realms, then to my mind, this would constitute a truly unverified belief, for there is no experience either individually or collectively that can be used to justify the existence of these undetectable things. We human beings can imagine the imaginary and the impossible. We can assign properties and characteristics to imaginary things and think logically and rationally about imagined things within the scope of their assigned properties. But unless and until it is experienced in some way, it can only be considered imaginary or hypothetical.
For me, the 'real world' hypothetical beliefs James uses and religious beliefs are entirely dissimilar and for that reason, the thesis fails.
As to James's concern over excessive skepticism, I do not share his concern. As described above, I do not see knowledge acquisition in James's stark dichotomy of seeking true beliefs and avoiding or rejecting error. The way that I see it, error correction is built in to the knowledge acquisition process. For me, skepticism is assuaged with experience. The longer a conclusion comports with our experience, skepticism will continue to fade. The more experiences that conflict with, or contradict a conclusion, the more skepticism will rise. It is this latter case that has prompted the need for James to defend religious belief.
As an aside, James's father, Henry James Sr., was a Swedenborgian Theologian, and I can't help but imagine that this may have played a significant role in the development of William James's strong religious belief, as belief is subjective, emotional, psychological.
But, says James, what if this is such a case where having the actual positive belief "I can make the jump" influences the proceedings so as to make itself true. "Very interesting," says James, and I think so too. Because it seems to propose that, in principle, unverified inflictiocan (sometimes) be true simply because it is believed prior.
This sounds like the self-help mantra, “The power of positive thinking!”, which I believe is a legitimate psychological phenomenon, akin to the placebo effect. Positive thinking may enable one to maximize their potential, but it will not enable one to exceed it, or exceed the laws of physics, or make something physically real and existent simply through ones will.
So, for our mountaineer, the prior belief about the jump is neither true nor false. It was simply a subjective opinion and limited in it's impact on the outcome. Just as an Olympic track athlete cannot consistently jump their record distance every single time, if James made the mountaineer make the jump repeatedly, what might the odds of success be? Not 100% if the jump was truly at the limits of our mountaineer. No, the fact that the mountaineer believed she could accomplish it and did on the first try should be attributed to luck, chance, or serendipity, not the power of unverified belief.