I still remember watching a science program about "life." It looked at the function of proteins, various kinds of molecules, and other such things. It went through many of the various and wonderful kinds of life that exist on our planet. However, it did not go much beyond the biological process, chemicals, and things of this nature. It left this impression that life is merely physical.
We live in a time when much of our science and philosophy is founded upon naturalism. In other words, anything beyond what you can touch, see, or test simply is not real. This excludes the supernatural, spiritual realities, and even God himself. Life is reduced to biology. Thoughts, emotions, and the will are reduced to brain chemicals. Life becomes nothing more than various types of chemical reactions. When it comes to a concept such as "life," isn't this what most people think of? You find life in a greenhouse, the zoo, in the ocean, the desert, and in the cities.
Most people, even unbelievers, believe on some level that human life is much more than biology. Simply being alive does not always qualify as life. Being what many people call a human vegetable is not what many people would classify as "life."
Jesus said that eternal life is knowing God (Jn 17:1-3). This demonstrates that eternal life is not merely about length, or existing forever. Several passages indicate God created humans to be immortal (Mk 9:44-48; Rev 14:11). Some will remain eternally in Heaven, which is life, others in Hell, which is death. Scripture never speaks of eternity in Hell as "life." Only fellowship with God is ever called "life" in scripture.
This means life is not about quantity and length, but quality, or depth, which is knowing God. Life is much more than biology. Animals have biological life as do plants and other types of creatures. However, only man has been created in the image of God. Life is something much deeper than biology for man. Life is harmony with God (Jn 12:50). Harmony with God also means harmony with your brethren:
"We know that we have passed out of death into life, because we love the brethren. He who does not love abides in death. Everyone who hates his brother is a murderer; and you know that no murderer has eternal life abiding in him" (1 Jn 3:14-15).
Do you have life? To answer that question, you must ask another: Do you know God? To find an answer to that question, you must ask this: Do you live in harmony with God and his will? To answer this question, you must ask this related question: Do you live in harmony with your brethren? All these questions are related to each other. Life is harmony with God, which means harmony with the brethren as well.