Originally published in the chapbook An Alternate History of the 21st Century, Spilt Milk Press, Summer 2007.

• Locus Recommended Reading List, November 2007
• To be reprinted in The Year's Best SF 13, edited by David G. Hartwell & Kathryn Cramer (Eos)

" 'Objective Impermeability in a Closed System' is an intense evocation of the ethical and emotional dilemmas of a scientist of whom idealism is expected but for whom compromise is easier.... A temporal paradox exists; AIs and a time machine become involved; but rather than the conventional circular narrative this implies, Shunn opts for an unusual, psychologically resonant conclusion, and a subtle questioning of the essentials of cause and effect. The implications run quite deep."

—Nick Gevers, Locus