In the October 7, 2010 edition of Nature (available online only to subscribers), one can read a short book review touching on “cosmic inflation,” as described by Stephen Hawking and Leonard Mlodinow.

Cosmic inflation is the process by which a small part of the very young universe blows up into a vast geometrically flat and almost-smooth patch large enough to encompass all we can see and more, thereby accounting for the universe around us today. [It] makes a number of predictions that have been verified. Yet because of quantum mechanics, inflation is not a one-time event but occurs continuously. Enormous bubbles of space-time are constantly being spawned, each one causally disconnected from the others and harboring its own laws of physics.

Fascinating, indeed, but is it science? Author of the book review, Michael Turner, writes that “cosmic inflation” gives him a headache. “It is science if we cannot test it? The different patches are incommunicado, so we will never be able to observe them.” Turner expresses hope that we will someday understand whether we are part of a multiverse. Then again, he worries that we might be “becoming the philosophers that Feynman warned about [in his 1964 messenger lectures].”

When has inquiry ceased being science and started becoming philosophy?

[Richard Feynman] warned that we should achieve the Ionian goal of finding all the laws, then”the philosophers who are always on the outside making stupid remarks will be able to close in,” trying to explain why those laws hold; and we won’t be able to”push them away” by asking for testable predictions of those ideas.