Science claims that the cells in our bodies are alive, but the fundamental parts of the cell such as molecules and atoms are not alive. Does that mean our bodies are only partly alive?
Science also says that some of the cells in our bodies are dead. That already implies that our bodies are only partly alive, but only in the sense that not every part of our bodies is alive. If every part of a living thing must be alive, then the fact that atoms and molecules aren't alive implies that none of our cells are alive, and no bodies are ever alive. Both of those consequences are false. So we must reject the principle that every part of a living thing must be alive.