There are thousands of Christian denominations. Clearly nobody knows what the truth is.

The framing is statistically misleading. (1) The 45,000 figure in the World Christian Encyclopedia counts every national affiliation separately: the Anglican Church of Kenya and the Anglican Church of Nigeria are counted as distinct denominations, though they share polity, liturgy, and confession. When you collapse those to actual doctrinal families, you get a much smaller number - broadly Catholic, Orthodox, Anglican, Lutheran, Reformed, Baptist, Methodist, Pentecostal, and a handful of others. (2) On essentials, historic Christianity has been extraordinarily united for 2,000 years: the Apostles' Creed and Nicene Creed (the Trinity, the incarnation, the resurrection, the forgiveness of sins, the life to come) are confessed by nearly every Christian tradition on earth. Disagreements cluster in the secondary and tertiary layers. (3) Comparison is fair: political philosophy, moral philosophy, and science itself contain deep internal disagreements without anyone concluding "nobody knows anything." Diversity within agreement on fundamentals is not chaos; it is the normal shape of a living tradition. (4) Jesus prayed for unity (John 17:21); the scandal of Christian division is real and biblically diagnosed. But the existence of division does not entail that no truth lies beneath it.