Robert C. Tucker said this quote

“ It will be seen how subjectivism and objectivism, spiritualism and materialism, activity and suffering, only lose their antithetical character, and thus their existence, as such antitheses in the social condition; it will be seen how the resolution of the theoretical antitheses is only possible in a practical way, by virtue of the practical energy of men. Their resolution is therefore by no means merely a problem of knowledge, but a real problem of life, which philosophy could not solve precisely because it conceived this problem as merely a theoretical one. ”