A science has predicitve power based on theory, but only if theory actually explains a phenomenon rather than describe it. Mainstream economics is inherently descriptive; Thomas Piketty chided economists for their fascination with math rather than the real world.

In the real world there are two types of firms: consumer and productive. They generate two economic circuits, one of buying and selling goods and services, the other of the production of said goods and services. These operate at different rates. A science of economics starts there. Read

For a New Policial Economy by Bernard Lonergan, Economics for Everyone by Philip McShane or anything by Michael shute.