Nothing from nothing = nothing. No doctrines are necessary.

I've not read Aronson's book, so my confusion must be qualified, so: Why must an atheist (like me) be compelled to articulate a “positive” approach, when atheism at root merely describes the absence of belief in unseeable, unknowable and unprovable supreme beings?

Negation is inevitable in the sense of my being without personal belief in phantasmogoria. When any such solid evidence in support of a deist perspective should appear, I'm ready to consider it. Until then, there is nothing.

It is superfluous for either deist or atheist to imply that atheism must present a “positive” platform or doctrine. Supernaturally speaking, nothing from nothing equals nothing. Unlike religion's confusing and contradictory directives, we as atheists neeedn't flail ineffectually in the search for something that can be artificially tied to supernatural sanction as stated by scatter-shot "holy" books.

Rather, the fundamental human-centered ("humanism" hardly can be considered a pejorative), reality-based considerations in any chat about "whither: mankind" remain in effect, just as they always have been, without muddying the debate with intrusions of imagined entities. Suggestions of atheistic platforms are tricks borne of dim semantic light, and I intend to avoid them.

spending a Sunday AM with a group of atheists

 ... The book, by Ron Aronson, is trying to encourage the search for a "positive" approach to atheism. Up to now, atheism has been largely "negative"-- what it's against, rather than what it's for. (In this, ironically, it resembles much of the Religious Right, especially in previous decades-- which has had the same problem, at least in terms of perception.)