The first altar mentioned in the Word was the one built by Noah after he came out of the ark, after being saved from the great flood. On that altar, he sacrificed clean animals to the Lord.

Mountains represent the Lord because of their height; we need to raise our thoughts above worldly things when "talking" with the Lord. An altar is a small artificial mountain. When it's used in worship, it can call to mind this raising of thought. The fire and smoke that rise from an altar are symbolically being sent to the Lord.

Most altars were made from unhewn stones. Stones represent truths. Unhewn stones - ones that have not been shaped by men - represent truths from the Word, truths that have not been adulterated.

The clean beasts to be sacrificed represent good things, charitable acts done because they are right. The clean birds represent thoughts about doctrine and actions, and about what is right. Presenting these things is an acknowledgment that we have them from the Lord, and a giving thanks to Him for them.

In the Israelitish Tabernacle, the altar of burnt offering represented the acknowledgment of good and the altar of incense that of truth. For this reason this larger altar, which was outside by the door, was made of brass which signifies natural good, while the altar of incense was made of gold, which signifies love to the Lord from whom comes truth.

3412. 'All the wells which his father's servants had dug in the days of Abraham his father, the Philistines stopped them up' means that people who possessed knowledge of cognitions did not wish to know interior truths that came from the Divine and so effaced them. This is clear from the meaning of 'wells' as truths, dealt with in 2702, 3096, here interior truths coming from the Divine since the wells, which mean truths, are said to have been dug by 'his father's servants in the days of Abraham his father' - 'Abraham' representing the Lord's Divine itself, 2011, 2833, 2836, 3251, 3305 (end); from the meaning of 'stopping up' as not wishing to know and so effacing; and from the representation of 'the Philistines' as people who possess no more than a knowledge of cognitions, dealt with in 1197, 1198.

[2] The subject at this point is the appearances of truth that belong to the lower degree, which are able to exist with those who possess a knowledge of cognitions and whom 'the Philistines' are used to mean here. With regard to the interior truths that come from the Divine and are effaced by those called the Philistines, the position is that in the Ancient Church and after it the name Philistines was used for those who gave little thought to life and very much to doctrine, and who in course of time even rejected matters of life and acknowledged matters of faith - which faith was separated from life - as being the essential element of the Church. As a consequence they attached no importance at all to matters of doctrine concerning charity which in the Ancient Church constituted the all of doctrine, and so they effaced it. Instead they proclaimed matters of doctrine concerning faith and centred the whole of their religion in these. And since in this way they departed from the life of charity, that is, from charity as the sum and substance of life, they more than all others were called 'the uncircumcised'. For by 'the uncircumcised' were meant all in whom charity was not present, no matter how much doctrine they knew, 2049 (end).

[3] Because such people departed from charity they also removed themselves from wisdom and intelligence, for no one can have a wise and intelligent discernment of what truth is unless good, that is, charity, reigns in him. Indeed all truth originates in good and has regard to good, so that anyone who is devoid of good is unable to have an intelligent discernment of truth, and does not even wish to know it. When such people in the next life are far away from heaven, light bright as snow is sometimes seen to be with them. But that light is like the light in wintertime which, being devoid of warmth, is unproductive. This also explains why, when such persons draw near to heaven, their light is converted into utter darkness, and their minds into something akin to that darkness, which is stupidity. From these considerations it may now be seen what is meant by the statement that people who possessed no more than a knowledge of cognitions did not wish to know interior truths that came from the Divine and so effaced them.