When Americans invoke the myth of exceptional upward mobility, we often imagine someone who strikes out on her own, transcending the limitations of her current circumstance by starting a business or getting a degree that affords far greater rewards. But ironically, such risk-taking requires security: the security of knowing that switching jobs or careers won’t get you deported. (Knowing that you won’t lose your healthcare helps too.) For millions of Americans, that’s what Obama’s immigration move makes possible.

As Obama himself has acknowledged, his unilateral action isn’t sufficient. While making some of the undocumented legal, it still won’t make them citizens. Until Congress acts, they will still represent a separate caste. But their opportunities for economic mobility—and with it cultural assimilation—have just shot up. Will those opportunities come at the expense of some other Americans, whose legal status had previously given them an economic advantage? Sure. But that’s the whole point of class mobility. When men and women becomes masters of their own fate rather than prisoners of circumstance, some rise and others fall.