Actually we can. Many of us are very well acquainted with the Bible (the real one) and God's very clear instruction to test spirits that speak to us against the word and our own ability to reason. He was very clear that the spirits of darkness will come in the veil of light and goodness to tempt and mislead us. That is why God gave us minds as well as emotions.
A reasoned minds knowns the words in the BOM and other LDS writings is not from God.
Compare reality to what your heart has been telling you. It will not add up, it can't.
reason is not the be all, end all. What does reason tell you about Christ’s resurrection? That it couldn’t happen, but yet it did. That He could not effect miracles. He did that, too.