These summaries address Summa Theologica part III, Q14 and 15 respectively.
Q14. Defects of body assumed by Christ
“My grace is sufficient for you, for my power is made perfect in weakness.” 2 Cor. 13:9
A1. Christ came to satisfy for the sin of mankind. The only way to do this was to take on the punishment due to sin, of which the bodily defects are part. So this did not hinder the Incarnation but was useful toward this end. Also, for people to believe in the Incarnation, Christ had to become fully human. A human being who doesn’t appear to suffer like others would not seem to be a real man, and indeed some early heresies (the Manicheans and Docetists) proposed just this sort of belief. Finally, by suffering Christ teaches us patience and fortitude.
A2. In considering whether Christ was subject to bodily defects by necessity, we have to consider necessity as both something imposed externally by another person against our nature and will and as something that is imposed by the very nature of a thing. It is the nature of flesh to be subject to hunger, thirst, sorrow, pain, and death. In this sense, Christ was subject to the defects of the body by necessity. However, while He willed His body to suffer these defects with both His Divine and human wills, the natural instinct of His human will would be against these defects. In this way, He was subject to bodily defects by necessity.
A3. The cause of death, hunger, illness, thirst, and other bodily defects is sin. In this sense, as all men except Christ are subject to sin, all men contract these defects. (In this, St. Thomas differed from the faithful in that he did not believe that the Blessed Mother was conceived without original sin but was sanctified after animation. See III, Q27.) However, in Christ, the cause (original sin) did not exist. While He had the defects attributed as an effect of sin in mankind, He assumed them willingly rather than had them thrust upon Him, knowing that through these weaknesses He would conquer sin.
A4. Christ assumed what was necessary to make satisfaction for sin. To do so, He needed the fullness of grace that His soul possessed. However, He did not assume those defects that would’ve been incompatible with perfection of knowledge and grace. In addition, other defects are caused by external factors due to the overall corruptibility of the body rather than as a direct result of sin (for example, bodily ailments or by defects during gestation). These are secondary defects rather than the primary defects of corruptibility and passibility. Christ was conceived by the Holy Spirit and endowed with every natural perfection. Those defects He assumed were those that are the condition of mankind due to sin, although in Him not caused by sin.
Q15. Defects of the soul assumed by Christ
A1. Christ assumed those defects that aided Him in proving the truth of His human nature and for providing and example of virtue. Sin would be a hindrance in both of these efforts since it impedes satisfaction of penalties for sin. In addition, sin is not natural to the human soul, so sin does not prove Christ’s humanity. Finally, sin itself is opposed to virtue, so it adds no value as an example except as an example for further sin.
A2. The moral virtues make the irrational parts of the soul subject to reason The more perfect the virtue, the more subject are the irrational aspects of the soul, of which concupiscence is part. While concupiscence is, according to Hardon, a “movement of the sensitive appetites” toward things one sees as pleasures and away from thing one sees as painful, it can also include inordinate desires, which here are called the “fomes of sin.” These are inclinations that are contrary to reason. Strong virtue weakens the influence of the fomes of sin, so it only makes sense that Christ, who had the virtues perfectly, would have no fomes of sin in Him. So while Christ had concupiscence to a degree (ad 2), He had it within right reason.
A3. We know from questions 9–12 that Christ had fullness of knowledge, and from question 7, the fullness of grace and virtue. While virtue excluded the possibility of fomes of sin, fullness of knowledge excludes the possibility of sin. Just as the fullness of virtue excludes the fomes of sin from Christ, so the fullness of knowledge excludes ignorance.
A4. A soul can be affected by both bodily and animal passions. The former refers to those aspects that disturb both body and soul, given that soul is the form of the body. Since Christ’s body was passible, it follows likewise that His soul was passible. In the animal passions, all of the sensitive appetites are properly considered passions of the soul, so Christ had these as well, just as He had all things pertaining to human nature. However, whereas these passions can become unruly and contrary to reason, in Christ this wasn’t so. He had the bodily and animal passions but always held them in check by way of reason.
A5. Christ possessed all of the qualities natural to a human nature, both in body and soul. Christ’s body was able to hurt since it was passible and mortal and since He possessed a human soul with all of its powers, so was able to suffer as the form suffers with the body. Thus He experienced true pain.
A6. Divine dispensation prevented the joy of the beatific vision from overwhelming the sensitive powers and reducing pain. Likewise, it prevented other effects of the sensitive appetites such as sorrow to be suppressed. Unlike pain, which affects the physical senses, sorrow addresses things that can be hurtful or evil interiorly as understood by reason or imagination. So just as He could suffer true pain, He could suffer true sorrow.
A7. There are two kinds of fear. One is an irrational fear of the unknown. The other is a reasonable fear of something that will likely cause pain. When the pain is imminent, then fear gives way to sorrow. When the threat of pain is still future and possibly avoidable, fear is a reasonable response. In this latter sense, Christ felt fear.
A8. We can wonder in different ways. If we wonder about causes we do not see or understand, we wonder due to our ignorance. However, we can also wonder in a speculative fashion about our experiences in order to draw deeper meaning from them. In this latter sense, Christ had the ability to wonder, even if to model for us how we should reflect on our experiences and come to greater understanding through them.
A9. Anger is a passion that arises from sorrow and a desire for revenge. Sometimes that desire for revenge can be irrational, which is sinful. Such a desire doesn’t exist in Christ. However, sometimes this desire for revenge is for due justice. In this sense, Christ did have this desire, as mentioned in John 2:17 and elsewhere. Since Christ also had sorrow, so together, Christ would have anger in Him. Anger motivated by a desire for justice is righteous or zealous anger and not sinful.
A10. Perfect beatitude pertains to both body and soul. It is clear that Christ’s mind had the beatific vision (called the science of vision by Ocáriz et al). Yet His body, which was passible and mortal, did not yet posses this. So in regards His soul, He was a comprehensor in all that was proper to it, but regarding the rest of His human nature, He was a wayfarer.