If farming is to be bearable it must be good to the environment and still support the needs of society. We are seeing more and more designs that attempt to do this and in cases where they come close to succeed there is greater attention to local, organic food that is accessible to everyone. There shall be no residual harm as a price for immediate return. From season to season the soil should be undepleted and the downstream clean and pure.
In order to achieve equitability the farm has to support society as well as the farm owner. Most western business models currently reward the investors and individual owners. However, more equitable association can be appreciated when farm profits are returned to the farm. When the profits are spread to more families by expanding the number of farmers that are able to provide.
It is viable when it endures, yields and functions in the capacity for which it was designed. Generally that entails that it does not require depend on unreliable sources, which could be related to weather, economy or operability. When the system or product delivers food year after year without requiring off site resources then in is viable in its productivity and can be relied upon.