For Grantaire, the revolution isn't the one that Enjolras is always talking about, the one that--somehow--through science and education will help the poor (and never ask who will pay for this), overturn Louis-Philippe (even though, as kings go, he's not that bad) and force the world to progress if they die (because people apparently never die in vain if they die for a good reason).

For him, the revolution is what happens inside him when he looks at Enjolras--not just because he craves the man (though he does, and wasn't that a shock to discover?), but because Enjolras cares fiercely about his cause and his country, stripping away mountains of cynicism from Grantaire, making him believe, not in the revolution, but that what Enjolras wants is worth having. He cannot believe in the revolution or the barricades; he cannot believe in his country as the glorious entity that Enjolras adores; but he can believe in and love and die for Enjolras with all of his skeptical, dubious, questioning heart, and that, he thinks, is a revolution indeed.