In The Giver by Lois Lowry, chapter 8, what four qualities made Jonas the perfect candidate?

The first quality that makes Jonas the perfect candidate to be the Receiver of Memory is wisdom.  Technically speaking, Jonas doesn't have this one . . . yet.  It is the one that he can and will acquire with training.  

The second quality that Jonas has is intelligence.  Jonas has shown through his work at school that he is a top student. 

The third quality is courage.  This quality is similar to the wisdom quality.  Jonas hasn't necessarily shown this quality a lot yet.  But both the chief elder and the current Receiver "feel certain that you [Jonas] are brave."  

The fourth quality is integrity.  Jonas has shown himself to be a good rule follower.  That doesn't mean Jonas is perfect, but Jonas has always been honest about his errors.  He confesses them and accepts the consequences.  

Technically, there is a 5th characteristic.  That characteristic is "the capacity to see beyond."  It's why Jonas can see things in color.  The current receiver also already confirmed that Jonas has this quality. 

What four qualities qualify Jonah for his new position in Chapter 8 of The Giver?

When Jonas receives his position of Receiver-in-training in Chapter 8 of The Giver, he isn't even sure what the title means. When the Chief Elder shares Jonas's assignment with the Community, she tells them that the position cannot be observed and that Jonas must live apart and alone. There is only one Receiver in each community, and it is the Receiver's job to train his successor. There is no room for error when selecting the next Receiver in their community, and the choice must be unanimously approved by the Committee.

The Chief Elder lists four different qualities that the Receiver-in-training must demonstrate when being considered for the position:

• Intelligence: Jonas has proven himself to be an intelligent student.
• Integrity: Jonas has inadvertently committed "minor transgressions" in their community, but he has always submitted himself to the required consequences.
• Courage: Since Jonas's community has never really felt true pain, they aren't even sure what the courage required of Jonas will demand. They can only ask for guidance from the current Receiver, who advises that the community cannot prepare Jonas for the tasks he will face. Nevertheless, the Chief Elder insists that they believe that Jonas is quite brave.
• Wisdom: The Committee believes that Jonas has the ability to acquire wisdom through the training he will complete in the days ahead.

The Chief Elder also mentions that the Receiver must have the Capacity to See Beyond, which she admits she does not understand; however, the current Receiver has indicated that Jonas already possesses this quality.

More specific rules governing Jonas's training are found in Chapter 9.