claim for truth 真理の要求
the will to truth 真理への意志

Upon hearing it's about Foucault's "L'order du discourse", I soon thought of a phrase 真理の探究, that is directly translated as "quest for truth" which may be deviated in the context. I guess both 真の要求 and 真理の主張 would be probably more suiting when we consider Foucault negates the role of knowledge to proove absolute truth, but his thought focuses on thinking how knowledge emerges and develops, referened on wikipedia introduction.

By the way, I once tried Foucault reading, but it was not a bit too hard, I know.

On the othe hand, 真理への意志, that is, the will to truth, appears to be a commonly used term in highschool ethics class text.