  Form is for Bacon a structural constituent of a natural entity or a key to its truth and operation, so that it comes near to natural law, without being reducible to causality. This appears all the more important, since Bacon—who seeks out exclusively causes which are necessary and sufficient for their effects—rejects Aristotle's four causes (his four types of explanation for a complete understanding of a phenomenon) on the grounds that the distribution into material, formal, efficient, and final causes does not work well and that they fail to advance the sciences (especially the final, efficient, and material causes). Consider again the passage quoted in Section 3.3: 