We are Heterogeneous
People are created with a wide variety of skills, needs and desires. In the Bible, we see this in God’s creation in his endowment of people with a wide variety of skills to build the tabernacle (Exodus 35:30-36:5) and to rebuild Jerusalem upon the return of the remnant from the Babylonian captivity (Ezra 7:6-7; Nehemiah 1, 2). Paul emphasizes that we are each gifted differently (1 Corinthians 12:12-31). In addition, since we were not all born at the same time, human society has a rich variety of ages and life stages. Some people are young and not yet able to provide their own food and shelter, others are just beginning to be able to do so, others are in their prime productive years and have resources in excess of their current needs, and still others are older and need help in supporting themselves, or need to draw on resources accumulated during their earlier years.
This heterogeneity is a foundation of financial markets because at any given time some people will have excess resources while others will have need or opportunity to use resources beyond what they currently possess. For example, some of us will want to borrow money to pursue a business opportunity or build infrastructure to fulfill some unmet need in society. Others will be savers at some periods of their lives and will be able to lend to meet that borrowing need.