A "field" in the Bible usually represents the Lord's church, and more specifically the desire for good within the church. It's where good things start, take root, and grow. When you have a desire to be a good person and to do good things, the natural first questions are "What does that mean?", "What should I do?", "What can I do?". You look for ideas, concepts, direction. Once you figure out something you want to do or a change you want to make in yourself, you seek specific knowledge. If you want to volunteer at a food pantry, say, you'd need to know whom to call, when they need help, where to go, what to bring. Armed with that knowhow, you're ready to get to work. That process could be compared to food production. You start with a field -- which is that desire to be good. Then you plant seeds -- those ideas and concepts. Those seeds sprout into plants -- the specific facts and knowledge needed for the task (easily seen in the food pantry example, but also true with deeper tasks like "being more tolerant of my co-workers" or "taking more time for prayer," or "consciously being a more loving spouse"). Finally, those plants produce food -- the actual good thing that you go and do. The Writings also say that in a number of cases a "field" represents the doctrine, or teachings, of the church. This sounds markedly different. The desire for good is emotional, a drive, a wanting; doctrine is a set of ideas. But for a church to be true, its doctrine must be centered on a desire for good, and must lead people toward doing what is good. So sound doctrine is actually closely bound up with the desire for good.

4018. 'In front of the flocks; and they came on heat as they came to drink' means even to the point of an intense desire in the affection for truth that a joining [to the goods and truths within the natural] might be effected. This is clear from the meaning of 'coming on heat as they came to drink' as an intense desire. The meaning of 'being on heat' as an intense desire is self-evident; and for the meaning of 'coming to drink' as the affection for truth, see immediately above in 4017. The reason why 'in front of the flocks' means that a joining to the truths and goods within the natural might be effected is that this phrase implies seeing and consequent arousal of affection, for this is the manner in which spiritual things are joined to a person. What is more, every implantation of truth or good in a person, as well as every joining of them to him, is effected by means of affection. The truths and goods which a person has learned but for which he has no affection do indeed enter the memory, but they are lodged there as insecurely as a feather on top of a wall which is blown off by the slightest puff of wind.

[2] As regards the things that enter the memory the position is this: Those for which there is no affection pass into the unlit parts of the memory when they enter it, whereas those for which there is affection pass into the light there. Things present in that light are seen and appear clearly and distinctly when any matter of a similar nature is brought up, but not so the things lying around in the unlit parts. Such is the effect that affection belonging to love has. From this it may be seen that all implanting of truth and joining of it to good is effected through affection; and the greater that affection, the stronger the tie joining the two together.

[3] The intense desire of the affection is in this case inmost affection. But truths are not capable of being implanted and joined to good except by means of affections for truth and good, which affections well up from charity towards the neighbour and love to the Lord as their sources. But evils and falsities are implanted by means of affections for evil and falsity, and these affections well up from self-love and love of the world as their sources. This being so, and the subject at this point in the internal sense being the joining of good and truth within the natural man, mention is therefore made here and in what follows of the flock being on heat when they came to drink, by which such considerations are meant.