Once again, The Times Magazine looks back on the past year from our favored perch: ideas. Like a magpie building its nest, we have hunted eclectically, though not without discrimination, for noteworthy notions of 2009 — the twigs and sticks and shiny paper scraps of human ingenuity, which, when collected and woven together, form a sort of cognitive shelter, in which the curious mind can incubate,