Take the case of gravity. Before Einstein, it was believed to be a force in the classical sense, but post-Einstein, our understanding is that gravity is not so much a force as an illusion of a force produced by the curvature of space-time.
So, while Brian Cox introduces forces as the 'agents of change" of the universe in the following video clip (and does a nice job of explaining the basic history behind their discovery, understanding an unification), one should still be aware that he's treading in conceptually dangerous territory, and that just like philosophy devoid of science is likely to get itself in trouble, science would be equally foolish to eschew the importance of philosophical analysis. Let's make love, not war :)
I'm kind of curious... whatever dark energy turns out to be, is it possible it might provide evidence of a hitherto unknown (and possibly even unsuspected) new force?