Science with its will to truth is not the antithesis to the ascetic ideal. Rather, Nietzsche suggests, the opposing force is found in the self-overcoming of the ascetic ideal, when the meaning of the will to truth is called into question.
Nietzsche concludes with the observation that our problem is not that we suffer but that we need to give meaning to our suffering. We cling to the ascetic ideal because it explains life to us; it explains why we must suffer. Granted, ascetic ideals direct the will against pleasure, beauty, even life itself, but it is still a will. And, Nietzsche says, returning to the point with which he opened the third essay, "man would rather will nothingness than not will."
We will recall Nietzsche's remark in section 12 of the second essay that all meaning, all interpretation, all "utility" is just a sign that a will to power is acting on a thing. Interpretation is not a neutral act. It is a matter of seeing a certain thing in a certain way or from a certain perspective. The perspective from which the thing is seen gives it a particular meaning or interpretation, and if a particular meaning or interpretation seems inseparably linked to the thing, that only means that a particular perspective has become overwhelmingly compelling.
It takes a will to interpret. In the case of a particular perspective being overwhelmingly compelling, there must be an overwhelmingly powerful will that is willing that interpretation. Nietzsche sees the ascetic ideal as an immensely powerful will that commands a particular interpretation of all life, all existence, and all history. It demands that we see ourselves as sinners and see life as suffering. It proclaims the strong to be evil and the meek to be good. It prescribes an ascetic lifestyle and an abstinence from earthly pleasures. Because this will has been so powerful and so dominant, it asserts itself as the only true will, the only true interpretation, and parades itself as absolute truth.
Nietzsche argues that there is a will driving everything and that science is no exception. Science is not self-sustaining because it does not contain its own will to power. In recording only facts, science shuns interpretation. Essentially, it is refusing to assert a will upon the objects of its study, to see them in a particular way. This does not mean that there is no will driving science, and it certainly does not mean that science is the antithesis of the ascetic ideal. Rather it means that science is not independent, that there must be some other will hidden behind it, driving it and motivating it.
Nietzsche identifies this will as the will to truth. Science denies all interpretations and questions all beliefs for the sake of the truth. However, Nietzsche notes that science never questions or doubts the value of truth itself. This unbending faith in absolute truth is only a disguised version of the ascetic priest's unbending faith in an absolute God.