How do we know the soul exists, if modern science doesn't acknowledge it?
"We can admittedly find nothing in physics or chemistry that has even a remote bearing on consciousness. Yet all of us know that there is such a thing as consciousness, simply because we have it ourselves. Hence consciousness must be part of nature, or, more generally, of reality, which means that, quite apart from the laws of physics and chemistry, as laid down in quantum theory, we must also consider laws of quite a different kind." —Niels Bohr, 1922 Nobel Laureate, Physics
All living beings—plants, animals, or humans—possess consciousness and exhibit it in varying degrees. Consciousness does not arise from matter but is a symptom of the soul, which is an irreducible element of reality. Try as they may, scientists cannot create life in a laboratory by mixing lifeless chemicals.
We are the conscious spiritual soul within the body, and our departure from the body is called death. The phrase “passed on” is, therefore, an accurate description of what takes place when someone dies.
Consciousness means self-awareness, or the sense of “I am.” It also means awareness of our own thoughts and sensations. No computer—no matter how sophisticated—is conscious.
Ordinary, material science can't detect spirit or its symptom—consciousness. They're beyond the scope of matter. Spirit can be studied, though, by spiritual science, such as that given in the Vedas.
In our original pure state, we are conscious of our eternal identity in relationship to God. Now our consciousness is absorbed in matter, and we think we are whatever body we inhabit at the moment.
Besides consciousness, other evidence suggests that our identity is separate from our bodies—for example, past-life memories and out-of-body experiences.
More on this topic in Bodies and souls