There is a substantial difference between knowing something and believing it. Belief is much more powerful as it goes beyond logic and connects with peoples sense of self.
This idea helps make clear why there is a stigma about mental illness. The anxious person or the depressed person can know that they are ill, that it is possible to not be ill, often the problem is that they don’t believe that they can be well. I suffered from anxiety, there were brief times when I wasn’t anxious, instead of knowing I was well, I believed it was merely a temporary respite. It was when I believed that there was nothing wrong with me, when I believed what I already knew rationally, did I become well. so the mental illness stigma is perhaps because healthy people don’t recognise the difference between knowing something to be true and believing it. Perhaps for the healthy, they believe they are well before they have developed an explanation for why they are well, belief comes before knowledge in this instance.
As a scientist I both know and believe in the theory of evolution. I know, because I have studied, read and observed the evidence and accept evolution as a rational, empirically produced explanation for the diversity of life on Earth. I believe, because I also accept the scientific process for discovering the laws of the physical universe, I accept the process as a valid way of generating truth.
Many scientists have difficulty understanding why those of religious faith lack a belief in evolution, indeed some of faith have difficulty believing in evolutionary theory. Religious faith is different to simple belief. Belief in God is different to beliefs about the physical universe, because belief perhaps comes before knowledge, rather than coming after knowledge. Religious belief connects to the self, before any empirical process of gathering knowledge. Faith concerns something beyond understanding of relationships in the physical observable universe. As a scientist I believe that it is possible for science to explain what God is, but that humanity may never establish a theory of everything. Sometimes, it is perhaps dangerous or less open to truth if belief comes before knowledge.
It is accepted that such theories as evolution or gravity are true. such truths can be established from raw data acquired from the physical universe. I believed these truths before I became a Christian and I know that there is no conflict between holding these beliefs in addition to religious beliefs, such as God having a role in the creation of the universe. The issue is perhaps that for some people the religious belief is more powerful to themselves than a mere rational piece of knowledge. To the atheist scientist, belief in scientific theory is more powerful than mere knowledge or understanding of religion, often atheists struggle looking beyond mere empirical understanding of the physical universe. To someone of faith, these powerful ideas can make the concept of evolution seem less important and hence less true. Yet people are not robots, they all harbour non-rational thoughts and ideas, the belief of humanists that there is perhaps, simply, that there is a physical explanation for these mental phenomena, but their belief may not be as strong as these less easy to break down logically ideas are not as fully explored, perhaps mentally acknowledged or as strongly believed. No individual person has a fully coherent explanation of themselves or the wider universe, yet every individual is on a journey to discovering truths.
I think I should point out, that I am in no way declaring any superiority for religious faith over atheism. What I am saying is that faith is worthwhile exploring. It is a question of balance, people choose what to invest our mental energies upon, there should be space for rational scientific inquiry as well as reflection on the question of faith.