When life begins is not a belief, but rather a fact based upon scientific principles. Two living cells merge to form a new one that undergoes growth and development by multiplication of these cells and specialization into tissues, organs and systems that function integratively. Check a high school basic biology book and the definitions are all there. Many one celled organisms are accepted as living. When they cause disease, we kill them with antibiotics. Independent viability does not define life. Confusing oneself about whether a fetus is alive or not allows one to justify abortion. And if one did not abort, this "unliving" thing would continue to grow. Tell me, how do nonliving things grow.