David Dickson and Exclusive Psalmody

While preparing my Sunday School class on Chapter 22 of the Westminster Confession ("Of Lawful Oaths and Vows"), I came across the following in David Dickson's Truth's Victory Over Error:

"Question 2. "Is an oath warranted by the word of God, under the New Testament, as well as under the Old, in matters of weight and moment?

Answer. Yes...[he then gives a list of reasons why this is so, and the ninth reason is:]

9th, Because we need not fear to imitate any thing which is done in heaven. Our Lord has taught us to pray, Thy will be done on earth as it is in heaven. But the angel, (says John, Rev. x. 5, 6.) which I saw stand upon the sea, and upon the earth, lifted up his hand to heaven, and swore by him that liveth for ever and ever. That angel calls himself our fellow servant, and of our brethren the prophets, and of them which keep the sayings of this book, Rev. xxii. 9. And therefore the angels being of the same fraternity with us, do not act under different dispensations from us."

The verses Dickson cites are: Revelation 10:5-6, "The angel whom I saw standing on the sea and on the land raised up his hand to heaven and swore by Him who lives forever and ever, who created heaven and the things that are in it, the earth and the things that are in it, and the sea and the things that are in it, that there should be delay no longer," and Revelation 22:9, "Then he said to me, 'See that you do not do that. For I am your fellow servant, and of your brethren the prophets, and of those who keep the words of this book. Worship God.'"

Now, the interesting this about this is:

1. Dickson was a contemporary of the Westminster Assembly, and his Truth's Victory Over Error is the first commentary on the Confession (and an excellent one, at that!). 
2. Not only was he a contemporary of the Assembly, but he was also an Exclusive Psalmist as most if not all Presbyterians were at that time. He makes this clear in his commentary on several Psalms. See, for example, his comments on Psalm 150.
3. Dickson's argument for the validity of swearing oaths runs thus:
1. We are not to fear imitating anything which is done in heaven
2. Angels in heaven swear oaths
3. Therefore, we too can swear oaths

If his argument is valid (which I think it is), can be applied to singing non-psalms just as easily as it could be applied to swearing of oaths. In Revelation 5:8-14, we read: 

"8 Now when He had taken the scroll, the four living creatures and the twenty-four elders fell down before the Lamb, each having a harp, and golden bowls full of incense, which are the prayers of the saints. 9 And they sang a new song, saying: 'You are worthy to take the scroll, and to open its seals; for You were slain, and have redeemed us to God by Your blood out of every tribe and tongue and people and nation, 10 And have made us kings and priests to our God; and we shall reign on the earth.'

11 Then I looked, and I heard the voice of many angels around the throne, the living creatures, and the elders; and the number of them was ten thousand times ten thousand, and thousands of thousands, 12 saying with a loud voice: 'Worthy is the Lamb who was slain to receive power and riches and wisdom, and strength and honor and glory and blessing!'

13 And every creature which is in heaven and on the earth and under the earth and such as are in the sea, and all that are in them, I heard saying: 'Blessing and honor and glory and power be to Him who sits on the throne, and to the Lamb, forever and ever!'

14 Then the four living creatures said, 'Amen!' And the twenty-four elders fell down and worshiped Him who lives forever and ever."

Note that those worshiping the Lamb in heaven sing a "new song" (verse 9. not a Psalm!) and they use harps (verse 8) in their worship.

 Then, in Revelation 14:1-5, we read:

"1 Then I looked, and behold, a Lamb standing on Mount Zion, and with Him one hundred and forty-four thousand, having His Father’s name written on their foreheads. 2 And I heard a voice from heaven, like the voice of many waters, and like the voice of loud thunder. And I heard the sound of harpists playing their harps. 3 They sang as it were a new song before the throne, before the four living creatures, and the elders; and no one could learn that song except the hundred and forty-four thousand who were redeemed from the earth. 4 These are the ones who were not defiled with women, for they are virgins. These are the ones who follow the Lamb wherever He goes. These were redeemed from among men, being firstfruits to God and to the Lamb. 5 And in their mouth was found no deceit, for they are without fault before the throne of God."

Again, those in heaven worshiping the Lamb sing a new song (verse 3) and their singing is accompanied by harps (verse 2).

Now, if we apply Dickson's argument to the worship we find in Revelation 5 and Revelation 14, we would have an argument like this:

1. We are not to fear imitating anything which is done in heaven
2. In heaven, new songs are sung to the Lord, and instruments are used in the worship of God
3. We, too, can sing new songs to the Lord and use instruments in the worship of God

I appreciate the vigor with which my Exclusive Psalmist brethren defend the worship of God; however, I believe they are inconsistent when applying what Scripture has to say about the worship of God, specifically in singing "new songs" and in using instruments to accompany the singing of the congregation. We are not to fear imitating anything which is done in heaven, and it is clear from Revelation that in heaven more than Psalms are sung, and they are not sung a capella.