I think on some level the only viable position is to at least allow for a tiny bit of room for human agency and the power of ideas. Otherwise, there’s not much reason to choose to pick up a radical text (or to choose to do much of anything!). Material conditions may give us a revolution, but we can’t leave the heavy work, the decisions, or what we do with our day up to material conditions.

I think you're both thinking about things the wrong way. Its not that a revolution is historically determined and that in the meantime we could just use our agency and ideas to do some good in the world or to prepare ourselves for said revolution. A revolution born out of material conditions, and the actions and ideas of individual agents are not independent of one another, they are one and the same - the revolution will only happen precisely because those agents involved have chosen to take the necessary steps to make it happen in the first place, and those agents will have chosen to take those steps because of the material reality of which they are a product. The development of history both produces the thoughts and actions of these agents and is then itself advanced by those thoughts and actions. In other words, even if historical materialism shows us that the revolution is an inevitability, it will still not fall from heaven, it will still need to be constructed by revolutionaries, there will still have to be people to carry it out and bring it to fruition.

I think that suggestions that revolutions are an inevitability that our agency has no or little involvement in not only misunderstands materialism but also kinda implies that we are external observers of this phenomenon, waiting for it to unfold in front of us rather than us being subsumed and acting within it. I feel that this kind of thinking can too often cause people to downplay the importance of their own actions and struggles and what they themselves can do to contribute towards building the revolutionary movement when really I think a proper understanding of materialism should encourage us to get involved in struggles and do what we can to contribute to building the revolution.

Materialism understood in this way, I don't think this work by Graeber and Wengrow can be considered idealist. Challenging capitalist myths and enabling people to grasp a different conception of history and of what the future might be - as this book seeks to do - is an important step in opening people up to more revolutionary ideas. This is particularly important in those who are not currently on the left, as expanding the number of people who share our views is quite obviously beneficial to the movement. I think drawing in people with different political views is something Graeber was particularly good at, especially with Bullshit Jobs, Debt, and now hopefully this book too. If none of us ever sought to change people's minds and left it entirely up to "material conditions" to do it for us, we'd never achieve anything.

"It is far more difficult —and far more precious— to be a revolutionary when the conditions for direct, open, really mass and really revolutionary struggle do not yet exist, to be able to champion the interests of the revolution (by propaganda, agitation and organisation) in non-revolutionary bodies, and quite often in downright reactionary bodies, in a non-revolutionary situation, among the masses who are incapable of immediately appreciating the need for revolutionary methods of action." - Lenin, 'Left Wing Communism'.