[2] The fact that these kinds of things are meant by 'the serpent's tail' is clear in John,

The locusts had tails like scorpions, and stings were in their tails, and their power, in order that they might do people harm. Rev 9:10.

'Tails like scorpions' and 'stings in the tails' are artful reasonings based on falsities by means of which they can convince and thereby damage people; and this is why it says that the power they have is 'to do people harm'.

[3] In the same author,

The horses' tails were like serpents, having heads; and by means of them they do harm. Rev 9:19.

Here likewise 'tails like serpents' stands for reasonings based on falsities by means of which they cause harm, especially as it is said that such tails were those of horses and had heads. For 'horses' and also 'head' mean the area of understanding in the mind, and therefore 'tails' here means the more artful kinds of reasonings against truths that are based on illusions and consequent falsities. These reasonings are the lowest, for the more artful the reasonings against truths are, the lower they are.

[4] In the same author,

The dragon's tail drew a third part of the stars of heaven and cast them down to the earth. Rev 12:4.

'The dragon's tail' stands in a similar way for reasonings based on falsities. 'The stars of heaven' stands for cognitions of goodness and truth, 'casting them down to the earth' for destroying them. The dragon is the serpent which uses reasonings based on falsities to lead people astray and which led astray in paradise 'the mother of living ones', who was Eve, because of the tree of knowledge, that is, by means of factual knowledge based on sensory evidence, thus on illusions. This is also made plain in John,

The great dragon was cast out, the serpent of old, who is called the devil and satan, who leads the whole world astray. Rev 12:9.

[5] The fact that 'the tail' in general is the separated sensory level of the mind which does not look upwards but downwards, thus not in a heavenly but an earthly direction, and that consequently it means falsity is clear in Isaiah,

Jehovah will cut off from Israel head and tail, the branch and the bulrush. The old and the honourable [in face] is the head, but the prophet, the teacher of a lie, is the tail. Isa 9:14, 15.

Here 'tail' plainly stands for falsity, which the Word calls 'a lie'. In the same prophet,

There will not be for Egypt [any] work which the head and tail, branch and bulrush, may do. Isa 19:15.

'Bulrush' stands for that which is lowest. In Moses,

So Jehovah will give you to be the head, and not to be the tail, in order that you may be tending only upwards, but not be tending downwards, when you obey the commandments of your God. Deut 18:13.

[6] 'The tail' stands for the lowest part which looks downwards or outwards, that is, in a worldly and earthly direction and not towards heaven and the Lord. For the interior parts of the human mind together with sensory levels are raised upwards by the Lord when a person is governed by the good of faith and charity. But if he is governed by evil and falsity, then the interior parts together with the sensory levels look downwards and so solely to things in the world. As a consequence he sheds his human nature and assumes a beast-like nature, for wild beasts look downwards or solely to things on earth. The person who looks downwards wills what is evil and thinks what is false, but one whom the Lord raises upwards wills what is good and thinks what is true. A raising by the Lord does in actual fact take place and therefore a removal from evils and falsities. Angels have the actual feeling of being raised up; it is like the force drawing things towards the centre of attraction, the centre being where the Lord is within His Sun. Angels have their heads raised in this direction, but those in hell their feet, so that the angels look upwards but those in hell downwards, 3641, 3643. In the same book,

The foreigner who is in the midst of you will rise above you, upwards more and more, but you will go down, downwards more and more; he will be the head, but you will be the tail. Deut 28:43, 44.

Here the meaning is similar. In Isaiah,

Say to him, Beware, and be quiet; do not fear, and do not let your heart become soft on account of the two tails of these smoking firebrands, on account of the blazing anger of Rezin and Syria, and the son of Remaliah. Isa 7:4.

'Rezin king of Syria' stands for cognitions or knowledge of what is evil, 'Syria' meaning cognitions of what is good, see 1232, 1234, 3680, and so in the contrary sense cognitions of what is evil; and 'the son of Remaliah king of Samaria' stands for knowledge or cognitions of what is false. The latter and the former kinds of cognitions are 'tails' because they constitute what is lowest. 'Smoking firebrands' stands for blazing anger.