The notes in study 3 section 2c on page 39 say '... the marriage relationship is taken as the fulfilment of God's purpose in creating us male and female.'
Is this suggesting that a single person isn't complete in person? Do they need to be in a marriage relationship in order to fulfil God's purpose in creating them female or male?
Doesn't Paul say in 1Cor 7:1 said that "it is good for a man not to marry". If we need to be in a marriage relationship to complete us, Paul would not say that "it is good for a man not to marry"?

Response

The question is a helpful one as it raises how we interpret the Genesis narrative. In Study 2 a key part of understanding any part of the Scriptures is the literary context of the passage. So Genesis 2 flows out of Genesis 1 and flows into Genesis 3. The question is asking about the comments on Gen 2:18-25 stated in the study notes. How do we approach this issue? Let me pose two key questions to frame our discussion:
• what does Genesis 1 say about the relationship of male and female?
: vs. 26-28 are crucial. They affirm
i) Creation of ‘man’ in God’s image and ‘man’ is spelt out as male and female i.e. both male and female are equally created in God’s image. Thus the concept of image refers to a plurality of male and female within the unity of humanity. Another way of expressing this is that God creates ‘man’ as a community (which reflects the nature of God as trinity – plurality in unity, a community of Father, Son and Spirit).

ii) ‘Man’ as created in God’s image means that ‘male and female’ are God’s representative on earth and are to rule over the created order – they are to fill the earth and rule the creation according to God’s character and purposes.

• how does Genesis 2 expand or explain the relationship of male and female?
i) The Genesis 1 creation account concludes on the note of rest (Gen 2:1-3). This leads us into the remainder of chapter 2 which helps the reader to understand what living in relationship with God and his world is like – or we could say, Genesis 2 expands the concept of living in God’s ‘rest’, i.e. enjoying life in an unspoiled relationship with God (this is the rest that Christ’s death and resurrection will finally bring sinners to experience cf. Matt 11:28-29, 12:1-7; Heb 4:8-11; Rev 21-22)

ii) Genesis 2 will fill out what ruling the world will involve
– work, care and authority as v. 15 along with vs. 19-20 highlight.

iii) But Genesis 2 also expands what ‘man’ as male and female means and how that will enable ‘man’ to obey the command of Gen 1:28
– ‘Be fruitful and increase in number …’
This issue is explored firstly in v.18 by addressing two concepts:
* God declares that it is ‘not good’ for man to be alone
– companionship is an essential feature of our nature (created as social beings)
* God will make a helper ‘suitable for him’ (i.e. matching him)
– this emphasises the complementarity of the sexes.
Then vs.19-20 show man’s aloneness and as a reader we too can feel with man what it means to be alone. Finally God fulfils his word and makes the helper suitable for man. This leads man’s great joy as expressed in poetic form (v.23) – ‘bone of my bones, flesh of my flesh … woman’.

iii) the conclusion of the narrative is vs.24f – a statement about marriage that is applicable not only to Adam and Eve but to all future marriages.

It is in the light of this overall context that the notes state ‘… and the marriage relationship is taken as the fulfilment of God’s purpose in creating us male and female (Gen 2:24).’ It is not a comment on every aspect of male/female relationships nor is it dealing with male and female in the light of rebellion and salvation in Christ.
Note the next sentence on p.39 which states, ‘Elsewhere in the Bible our need for satisfying interpersonal relationships more generally is stressed.’
What is being affirmed is that the creation mandate of Gen 1:26-28 for ‘man’ will be fulfilled in the marriage relationship – single people are involved in the ongoing outworking of this creation mandate (e.g. ruling) but in its totality marriage is required.

Just a couple of other comments:
i) the question has suggested the notes are dealing with the concept of ‘completion’ as an individual but that is not on view in the creation account.
ii) literary context is vital when reading Paul’s arguments in his letters. So 1 Cor 7:1 begins Paul’s response to the matters that have come to him from the Corinthian church. Hence the comment, ‘It is good for a man not to marry’(NIV translation of Greek “it is good for a man not to touch a woman”) is what the Corinthians have written about, not a viewpoint that Paul is advocating. Though a quick read of the whole chapter may seem to indicate that Paul held a similar position his argument is not so simple. Paul is seeking to answer a number of issues that the Corinthians have written to him about. His answer is shaped by the concern to live in a godly manner – i.e. to have wholehearted devotion to the Lord. So he counsels the married, the unmarried, the “virgins,” and the widows to base their priorities in life on this concern. He suggests that wholehearted devotion to the Lord is best served by reducing major changes in one’s life situation, especially in times of crisis (Gen 7:26). So Christians should avoid, if possible, changes in their life situation (cf. Gen 7:2, 8, 10, 11).

Traditionally Moses has been seen as the author of the Pentateuch (first five books of the Bible). But there are indications that at least another person was involved in some way. We see this in …

a) Statements later than Moses (or probably not by him):

• The account of his death (Deut. 34).
• Comments inconsistent with Moses’ modesty:
• Exod. 11, ‘the man Moses was very great in the land of Egypt’;
• Num. 12, ‘Now the man Moses was very meek, more than all the men that were on the face of the earth.’

b) Statements after the conquest

• ‘Dan’ in Gen. 14 and Deut. 34. This northern city was called Leshem/Laish until by the Danites sometime in the period of the judges (cf. Josh. 19; Judg. 18).
• Lev. 18 and Deut. 2 refer to the conquest as having already taken place.
• Num. 32 describes the later activities of the Transjordan tribes.

c) Other later statements:

• The phrase ‘before any king reigned over the Israelites’ (Gen. 36) suggests acquaintance with the monarchy.
• Ancient place names which have become obsolete are explained, for example Kiriath Arba as Hebron (Gen. 23); Ephrath as Bethlehem (Gen. 35).
  

From this list of post-Mosaic references it would appear that there was at least some later editing of the books. But the list is small when compared to the length of the Pentateuch as a whole. So this editing is simply minor scribal additions and explanations to the books. They don’t substantially affect the basic issue of Moses as the author.