The inventory of processes that miRNAs regulate has continued to expand since their relatively recent discovery. A new study reveals not only that the expression of miRNAs changes with age, but also that these miRNAs can act in both pro- and anti-longevity regulatory pathways.

There is a puzzle about the truth of counterfactual conditionals in deterministic worlds. It is natural to suppose that if things had gone differently in the recent past—if, say, you had blinked one more time than you actually did while reading the previous sentence—the state of the world in the distant past would still have been exactly as it actually was. It is also natural to suppose that if...

Two things about Hilary Putnam have not changed throughout his career: some (including Putnam himself) have regarded him as a “realist” and some have seen him as a philosopher who changed his positions (certainly with respect to realism) almost continually. Apparently, what realism meant to him in the 1960s, in the late seventies and eighties, and in the nineties, respectively, are quite differ...