In Genesis 49:17, Psalm 58:4, Psalm 91:13, an adder signifies reasoning from the senses. (Arcana Coelestia 6398) In Isaiah 14:29, here, an adder also signifies the doctrine of three persons in the Godhead and of imputative faith applied to all, one by one. (Doctrine Regarding Faith 53, True Christian Religion 4874) In Deuteronomy 32:33, dragons and asps signify the sensual principles which form the basis of the natural man and are full of abominable evils with self-confirming falsities. (Arcana Coelestia 9013[3], Apocalypse Explained 5197)

In Isaiah 11:8, this signifies people who act craftily against innocence. People in the good of innocence need have no fear, for they are protected by the Lord. (Apocalypse Explained 4109)

(Odkazy: Apocalypse Explained 714)

6398. 'Dan will be a serpent on the road' means their reasoning regarding truth, since good does not as yet lead them. This is clear from the representation of 'Dan' as those guided by truth but not as yet by good, dealt with above in 6396; from the meaning of 'a serpent' as reasoning based on sensory evidence, dealt with below; and from the meaning of 'the road' as truth, dealt with in 627, 2733. Thus 'Dan is a serpent on the road' means their reasoning regarding truth, since good does not as yet lead them. The nature of that reasoning and the nature of the truth resulting from it will be stated below.

[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. Matthew 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.