The idea that biologists have difficulty with abstractions probably reflects the “solidity” of modern molecular biology. Biologists were doing genetics, working out the rules of heredity, mapping genes onto chromosomes, understanding meiotic cross-over, for decades before the physical nature of the gene was understood. Likewise immunology is full of terms and factors that today have a biochemical explanation, but again, for years only existed as abstractions. Biology is much easier to understand today, now that we have molecules for almost everything. But biologists did decades of very insightful and productive work that was completely based on abstractions.