If we endeavor to form our conceptions upon history and life, we remark three classes of men. The first consists of those for whom the chief thing is the qualities of feelings. These men create art. The second consists of the practical men, who carry on the business of the world. They respect nothing but power, and respect power only so far as it [is] exercized. The third class consists of men to whom nothing seems great but reason. If force interests them, it is not in its exertion, but in that it has a reason and a law. For men of the first class, nature is a picture; for men of the second class, it is an opportunity; for men of the third class, it is a cosmos, so admirable, that to penetrate to its ways seems to them the only thing that makes life worth living. These are the men whom we see possessed by a passion to learn, just as other men have a passion to teach and to disseminate their influence. If they do not give themselves over completely to their passion to learn, it is because they exercise self-control. Those are the natural scientific men; and they are the only men that have any real success in scientific research.
Peirce: CP 1.44 Cross-Ref:††
It seems to me that Brent ( Charles Sanders Peirce (Enlarged Edition), Revised and Enlarged Edition: A Life (9780253211613): Joseph Brent: Books http://buff.ly/1wrqgFL ) explicitly and Peirce implicitly does suggest that an icon is first, an index second and a symbol third. It also seems to me that there is no area of Peirce that remains as much subject to subjectivity as discussion around the many permutations of 1, 2 and 3.
Triadic Philosophy ( Changing Your Heart and Mind: Triadic Philosophy in A Nut Shell http://buff.ly/1zjdZB6) sees Signs as what initiates thought, what gets translated into something explicit in the mind. Firsts. Indices are a second step – a challenging set of explicit barriers or modifiers or protections. Seconds. Symbols are expressions and actions on the way to becoming reality (the fruits by which we are known). Thirds.
Since Triadic Philosophy at this point is merely my musings, not the subject of serious interest or discussion, it might be said to be ephemeral But it grows nonetheless. At the moment it is concerned to wrest from Aristotle his odd grip on ethics which he persists in presenting as a list of virtues, to the detriment of the measurability of actions and expressions, among other things.