9726. 'And you shall make for it a grating, a network' means the level of sensory perception, which is the last and lowest. This is clear from the meaning of 'a grating, a network' as external sensory perception, thus that which forms for a person the last and lowest level of life; and since this lowest level is meant by the grating it was placed all the way round the altar. Such sensory perception was represented by the grating because it first sifts so to speak and sorts out those things which enter the human mind and present themselves to the understanding and will, namely truths and forms of good. If the sensory perception is composed of good it does not let anything through other than forms of good, and truths derived from good, and rejects evils and the falsities arising from evil. For sensory perception is the actual ability to perceive things which belong to the understanding and to sense those which belong to the will as they exist on outermost levels, an ability that is perfectly fashioned for the affections for those things. The nature of all this may be illustrated by very many things in the body. Everywhere in the outermost parts within the body there are forms that resemble nets and there are so to speak gratings which sort out the things that flow towards them from the world. Those that are suitable are let through because they are desirable, and those that are unsuitable are rejected because they are loathsome. Extremely sensitive systems such as these exist in the stomach. These let through into the blood the suitable juices of the chyle, because these juices are useful and therefore desirable, and reject the unsuitable because they are harmful and therefore loathsome. The situation is similar with sensory perception, which is the last and lowest level of a person's life. But this level with a person has become totally wrecked, the reason why being that it stands right next to and is exposed to the world and is therefore the last to be regenerated, indeed scarcely anyone at the present day is able to be regenerated down to that level. As regards what the level of sensory perception is like with these people, see what has been shown already concerning it in 4009, 5077, 5081, 5084, 5094, 5125, 5128, 5580, 5767, 5774, 6183, 6201, 6310-6318, 6564, 6598, 6612, 6614, 6622, 6624, 6844, 6845, 6948, 6949, 7442, 7645, 7693, 9212, 9216.

Therefore if a person is to see and have an understanding of the truths of faith and the forms of the good of love he must be raised by the Lord above that level to more internal levels. But the sensory perception meant by 'the grating, the network' around the altar is the sensory perception belonging to the Lord's Divine Human, since the altar is representative of the Lord and of the worship of Him that springs from the good of love, 9714.

5774. 'And each one loaded his ass, and they returned to the city' means that truths were brought back up from sensory impressions to known facts. This is clear from the meaning of an ass' as factual knowledge, dealt with in 5492, and of 'loading' it as bringing back up from sensory impressions since 'causing one's pouch to come down to the earth' means bringing the contents of the natural down to the level of sensory impressions, 5767 (raising 'the pouch' up from these is what 'loading' implies here); and from the meaning of 'the city' as truth present in doctrine, dealt with in 402, 2449, 2947, 3216.

[2] A brief explanation must be given of what bringing truths back up from sensory impressions to known facts is. Sensory impressions are one thing, known facts another, and truths yet another; they are consecutive to one another, for sensory impressions give rise to factual knowledge, and factual knowledge leads on to truths. Images that come in through the senses are stored in a person's memory; then he uses those images either to deduce a fact or to gain a perception of some fact he is learning about. After that he uses these facts either to deduce certain truths or to gain a perception of some truth he is learning about. This is the way everyone develops onwards from childhood. While he is a child a person's thought and grasp of things relies on sensory impressions; as he grows older his thought and grasp of things relies on factual knowledge, and after that on truths. This is the path leading to the power of judgement a person enters into as he matures.

[3] From this one may see that sensory impressions, known facts, and truths are distinct and separate. Indeed the three remain so distinct that sometimes a person's attention is fixed on sensory impressions, as happens when he gives thought only to what impinges on his senses; sometimes his attention is fixed on facts, as happens when he rises above sensory impressions and thinks more deeply; and at other times his attention is fixed on truths which have been inferred from facts, as happens when he thinks more deeply still. Anyone who stops to reflect can know these things from what is present within himself. In addition a person can bring truths down into known facts and see those truths within them, even as he can bring facts down into sensory impressions and consider them within these. And he can do the opposite. From all this one may see what is meant by bringing the contents of the natural down to the level of sensory impressions, and bringing truths back up from sensory impressions to known facts.