God is knowable and trustworthy, and certainty can be had experientially, existentially, if our hearts are right. From another discussion:
And a favorite quote from the end of Tim Keller’s book, The Reason for God:
During a dark time in her life, a woman in my congregation complained that she had prayed over and over, “God, help me find you,” but had gotten nowhere. A Christian friend suggested to her that she might change her prayer to, “God, come and find me. After all, you are the Good Shepherd who goes looking for the lost sheep.” She concluded when she was recounting this to me, “The only reason I can tell you this story is—he did.”