Schopenhauer would disagree. In his world model the Will with capital W is probably best described as the driving force behind all movement. While abstract, it has concrete species (think color vs red, where color is will, and red is your concrete human will, that you can feel concretely by pinching your finger). About freedom of the will Schopenhauer also has a clear opinion: will is free in the sense of uncaused, random. That does not help humans though, because while they can do what they want, they cannot want what they want. I'm not saying that this is a good model, but it's quite concrete. Nietzsche build on it, Einstein had a portrait of him in his Berlin study alongside Faraday and Maxwell, and while Freud denied any influence, there are a lot of topics in common between them.