When Barry Allen uttered the words “There is no Flash without Iris West,” he wasn’t just waxing poetic for the sake of it. He doesn’t seem to be able to function much without her. Consider, for example, when he attempted to recreate the conditions in which he gained his powers, in order to get them back, but was instead, thrust into the Speedforce. While there, physical manifestations of the Speedforce took the shape of people he knew in real life and put him through a series of tests. Long story short, he couldn't return back to the real world until he caught a mysterious figure that kept running away from him. At the climax of the episode, Iris West eventually ended up relaying a message of hope to Barry inside of the speed force, which proved to be the anchor that brought him home.