Sustainability can be defined literally as the ability to be sustained, or the ability to endure or exist indefinitely. Sustainability is popularly considered to be just environmental sustainability, which is the capacity of something to sustain the environment. However, there are also other kinds and degrees of sustainability, such as social sustainability (the capacity of people, organizations and societies to be sustained), and economic sustainability (the sustainable management, distribution, and use of resources).
Society cannot exist without the environment, and the economy cannot exist without society and the environment. In other words, society is a subset of the environment, and the economy is a subset of society. Therefore, it is important that humans do their best to be responsible stewards of the environment, while also doing their best to sustain themselves, society, and the economy.
If sustainability is defined only as the ability to exist indefinitely, then it may be argued that living sustainably is not the end goal of life. Would someone want to exist in sorrow, or be unconscious but exist? No, life is seeking a joyous, conscious existence. Therefore, it may be said that the goal of life is to seek an ever-existing, ever-conscious, ever-new joy. Part of that goal is to find the most effective methods to achieve it. Whether there exists in man’s vocabulary an adverb to express that way of life is another question. Perhaps the best adverb is spiritually.
True sustainability requires not only environmental sustainability but also social and economic sustainability. True sustainability consists in being able to exist for eternity. People have said that it is only God and saints that are in attunement with Him who are able to exist for eternity. More than that, people say that God exists for eternity in ever new bliss. Saints say that souls will never be satisfied until we have that unceasing at-one-ment with God.