We must be able to doubt ourselves when necessary, to be certain when necessary, submitting ourselves when necessary. He who does not act thus understands not the force of reason. There are some who violate these three rules, either by asserting everything as demonstrative, through failure to understand what demonstration is; or by doubting everything, through failure to understand when they ought to submit; or by submitting in everything, through failure to understand when they should judge.
If we submit everything to reason, there will be nothing mysterious or supernatural about our religion. If we offend against the principles of reason, our religion will be absurd and ridiculous.