"It is the spirit that gives life, the flesh is of no avail; the words that I have spoken to you are spirit and life."
—John 6:63, Revised Standard Version Catholic Edition
They claim that verse 63 makes the entire discourse to be understood as symbolic, where Christ contrasted "flesh" between "spirit". One Protestant argued that "He was speaking were spiritual words when talking about eating his flesh and drinking his blood:" (Matt Slick, "Transubstantiation and the Real Presence", CARM). However, this is a complete misunderstanding of this verse. The Bible uses "flesh" and "spirit" as symbolizing the sinful human nature and the human soul in the state of grace. The usage of this is seen in Matthew 26:41; Romans 7:5-6, 25, 8:1-14; 1 Corinthians 5:5; 2 Corinthians 7:1; Galatians 3:3, 4:28, 5:13-26; and 1 Peter 3:18, 4:6. What Christ meant was that His words were only accepted by men who are filled with the Holy Spirit. The soul outside of grace and in grace. Christ here says that human comprehension cannot understand this unless the soul is aided by the Holy Spirit. Christ showed them that the Holy Spirit enlightens our minds, "But the Counselor, the Holy Spirit, whom the Father will send in my name, he will teach you all things, and bring to your remembrance all that I have said to you." (John 14:26, RSVCE). He simply stated that those who can accept or understand this is filled with the "Spirit of wisdom and understanding" (Isaiah 11:2). Human reason is unable to understand this truth apart from faith and the Holy Spirit (John 8:15). The understanding of verse 63 as being such is supported by the verse after that. The understanding that men who accepted Christ's words were men endowed with God's Grace. Christ could not have spoken concerning His flesh here. If He was referring to His flesh, He would contradict Himself. He clearly said that His flesh truly gives life (John 6:51; Ephesians 2:13-16; Hebrew 10:10). Therefore, what Christ meant was that they needed to understand His words through faith, not human understanding nor logic.
"But there are some of you that do not believe.” For Jesus knew from the first who those were that did not believe, and who it was that should betray him."
—John 6:64
The disciples that left Christ understood Him correctly, that is why He emphasizes on it and added His blood. In verse 52 the Jews disputed on the meaning of His words, "The Jews then disputed among themselves, saying, “How can this man give us his flesh to eat?” (John 6:52). Prior to this Christ did not mention the drinking of His blood. It is an interesting thing that Christ did not try to explain this, but repeated what He said and added His blood into the requirements. Christ emphasized on the eating of His flesh. In the original text of John 6:54, Christ uses the Greek word "trōgōn" (τρώγων). The Greek word "Trōgō" is a verb that means "chew" or "gnaw". This word is used in Greek literature to describe animal eating, animals like mules, cattle, pigs, and some cases humans. Jesus used this words in John 6:54, 56, 57, 58. This is an interesting note because Jesus used a different word. Prior to this Christ used the common verb for eating, "esthiō" (ἐσθίω) (John 6:49, 50, 51, 53). The change is very clear that Christ emphasized the eating of His flesh. He changed the focus from the necessity of faith to the eating of his flesh. He adds a greater force by using that verb.
The disciples that left Christ clearly understood Him, that He was to be taken literal. He did not try to explain to them. If He was speaking symbolically and that those that left Him understood Him literally, why didn't He explain to them if it were symbolic? Aside from not explaining, He repeated and added the drinking of His blood to it. In John 3:1-15, Christ explains to Nicodemus who took Christ's words of becoming "born again" literally. Christ explained to Nicodemus the symbolic or metaphorical meaning of it. Whenever there was a doubt pr misunderstanding, Christ explained what He meant to people who truly sought the truth (John 3:11-15). In John 6, the people's mind were closed from receiving the Spirit. It is because of that He did not explain to them like what Christ has done with Nicodemus.
