The field is the world (o de agro estin o kosmo). The article with both "field" and "world" in Greek means that subject and predicate are coextensive and so interchangeable. It is extremely important to understand that both the good seed and the darnel (tares) are sown in the world, not in the Kingdom, not in the church. The separation comes at the consummation of the age (sunteleia aiwno, Psalms 39 ), the harvest time. They all grow together in the field (the world).