What Aquinas Meant About Souls Surviving Death

The key question about pertaining to surviving death involved whether or not a soul constituted a substance to day. We think of substances as a kind of material like air, water and earth are substances. But that's not what aquinas and other philosophers of the period meant by the term 'substance' And anything that can exist on its own would be a substance. So animals and plant and animal souls aren't continuing things that can survive the death of the body.