[2] The reason why 'a serpent' means reasoning based on sensory evidence is that the interiors of a person are represented in heaven by living creatures of various kinds, and therefore in the Word similar things are meant by those same creatures. A person's sensory powers have come to be represented by serpents because they are the lowest of his mental powers. Compared with other mental powers those of the senses are on the ground so to speak, crawling around there, as may also be recognized from the forms that sensory impressions adopt when they enter in, which will in the Lord's Divine mercy be dealt with elsewhere. This explains why those sensory powers have come to be represented by 'serpents', so much so that the Lord's Divine sensory perception was represented by the bronze serpent in the wilderness, 4211 (end).

[3] True shrewdness and circumspection - qualities that reveal themselves in external affairs - were also meant by 'serpents', in Matthew,

Be shrewd as serpents and simple as doves. Matt 10:16.

But in the case of a person who is governed by his senses and is far removed from what is internal - as those people are who are guided by truth but not as yet by good - and who speaks as his senses tell him, 'a serpent' means false reasoning. This therefore is why here, where Dan is the subject, reasoning regarding truth because good does not as yet lead him is meant. In other contexts ill-will, deceitfulness, and trickery are also meant by 'serpents', though in those places they are poisonous serpents - such as vipers and the like - whose reasoning is their poison.

'A serpent' is reasoning based on sensory evidence, see 195-197.

'A serpent' is all evil in general, and evils are distinguished from one another by different kinds of serpents, 251, 254, 257.