I originally planned to write just two posts analyzing the physiological swoon theory, one devoted to the a priori arguments (see here) and one to the a posteriori. But upon further reflection I realized that the a posteriori arguments raise issues regarding the interpretation of the Gospels that are too involved to be dealt with in just one post. So I will deal with each of those arguments in a separate post each, starting with one of the lynch-pins of most conspiracy theories about Jesus' death: that the drink he was given on the cross was 'spiked' with some kind of drug that caused him to lapse into unconsciousness, so that he would only appear to have died, allowing Joseph of Arimathea and his fellow conspirators to take him down early from the cross and help him recover.
First, a few words about the proper interpretation of the Gospels is in order. Obviously for this or any other conspiracy argument to work, we have to assume that the Gospels essentially give us thoroughly detailed snap-shots of events in the life of Jesus, such that if we were to travel back in time and watch those events, they would unfold exactly as described in the Gospels. However, scholars have known for a long time that, even though the evangelists had the will and the means to convey accurate historical information about Jesus, ancient biographical conventions were quite different than modern ones. Ancient biographers were not interested in the same sorts of details as are modern scholars, and the details they did include were heavily shaped by the author's literary (or in the case of the Gospels, theological) concerns. The aim of ancient biographers was to illustrate the words and deeds of their central character in order to give their readers a full understanding of who that person was through their characteristic words and deeds. This could be done by narrating events and sayings which may not have unfolded exactly as described, but instead were characteristic of the person. We should be cautious, then, about assuming the eyewitness veracity of every single detail in the Gospel narratives, even if ultimately the Gospels were (and I believe they were) based on eyewitness information (for more on the Gospels as ancient biography see David Aune, The New Testament in its Literary Environment, pp. 17-76 and especially Richard Burridge, What Are The Gospels?).
In the case of the Passion narratives we can assume that the evangelists did want to convey accurate and detailed information about those events, as they explain most fully the nature of Jesus' mission and why he was killed. We have to keep in mind, however, that these narratives are also saturated with Biblical symbolism, as the early Christians found great scriptural significance in Jesus' death (Paul tells us that Jesus died for our sins "in accordance with the Scriptures," 1 Corinthians 15:3). Raymond Brown offers the following caution about doctors and other researchers who are not biblical scholars and who try to either diagnose the exact cause of Jesus' death on the cross or infer that he may have survived: "Often the medical writers have expressed their conclusions without recognizing that any or all of these features might embody theological symbolism rather than historical description." (R. Brown, The Death of the Messiah, Vol.2, p.1089)
Was the drink Jesus was offered on the cross a historical event or theological symbolism? There is evidence for both views. On the one hand, in Psalm 69:22 we have a complaint from the suffering just man about his enemies: "And they gave for my bread gall, and for my thirst they gave me to drink vinegar," suggesting that the evangelists are alluding to a scriptural motif. On the other hand, an offering of wine mixed with myrrh (as in Mark 15:23) is attested as a common practice before an execution. Talmudic sources tell us of a rabbinic dictum: "When one is led out to execution, he is given a goblet of wine containing a grain of frankincense, in order to benumb his senses...And it has also been taught; The noble women in Jerusalem used to donate and bring it." (Tractate Sanhedrin 43a; this could account for Luke's reference to the 'daughters of Jerusalem' accompanying Jesus to the cross). I think it's likely that this event actually happened and that the Scriptural allusion (made explicit by Matthew in his replacement of Mark's myrrh with the biblical 'gall' or χολη) was added over it. At first glance this might appear to increase the plausibility of Jesus' drink having been spiked, but there are more exegetical issues to be considered.
There are three separate narratives of Jesus being offered a drink recorded in the Gospels: an initial offering just before the crucifixion (Mark 15:23; Matthew 27:34) which Jesus refuses to drink (Mark says simply that Jesus refused, while Matthew adds that Jesus first tasted the drink before refusing it); a second offering after Jesus' cry of desolation (Mark 15:36; Matthew 27:48) or simply at some point before Jesus' death (Luke 23:36); and a third offering, recorded only in John 19:30, which Jesus actually requested himself and accepts. It is clear that each account has been decisively shaped by the individual literary interest of the evangelists, but noteworthy for our purposes is that only John has Jesus explicitly accept a drink at any point in the Passion narrative, and this was simply the sour, vinegary wine that was probably on hand for the soldiers to drink, not wine mixed with myrrh or any other suspicious substance.
I think the most likely harmonization of the accounts is that there were two offerings, the first of which Jesus did not accept and the second of which he did as in the Gospel of John. Matthew, Mark and Luke do not actually say whether Jesus accepted the second offering or not, they simply note the offer and then continue with Jesus crying out loud and then dying. But here another important factor must be considered: the differing motives behind each offer. The initial offering can be interpreted either as an act of mercy in line with the rabbinic tradition quoted above, or as part of the soldiers' ongoing mockery of Jesus as the 'king of the Jews': Pliny tells us that "The wines that were the most esteemed among the ancient Romans were those perfumed with myrrh" (Natural History 14.15), so the soldiers may have been offering such prized wine, certainly fit for a king, in order to carry on their parody of Jesus' kingship. If the offered sweet wine was an act of mercy, Jesus probably did not drink it because of his commitment to drink the full cup of suffering his Father had ordained for him (e.g. Mark 14:36; cf. Brown, Death, pp. 941-942). If the wine was an act of mockery Jesus refused to drink obviously because he would not feel like assenting to it. This explains Matthew's detail that Jesus tasted the wine before refusing it. The wine may have been particularly bitter and, once Jesus realized what was going on, refused to drink any more. Whatever the interpretation, Jesus rejected this first offering.
The Synoptics have either a passerby or a soldier offering Jesus the wine the second time, whereas in John Jesus specifically requests the drink. Again the reasons for this discrepancy are probably to be found in the individual literary and theological interests of the evangelists. In Matthew and Mark a passerby offers Jesus the drink after his cry of dereliction ("My God, my God, why have you forsaken me?"), so the person offering the drink presumably did so as a spontaneous reaction to a victim's apparent cry for help. In John Jesus requests the drink "in order to fulfill the scripture." It is unclear exactly what Scripture would be fulfilled, but in any case the difference remains. Following the hypothesis of this post, Jesus probably drunk the second time a drink was offered, just before his death.
It might seem a little suspicious then that Jesus died right after accepting this second drink. Could it be that the drink was laced with some kind of drug that rendered Jesus unconscious, only seeming to be dead? The probability of this is close to zero for several reasons.
First of all, the only offered drink in which specific additives to the wine are mentioned is the first, which Jesus refused to drink, and in any case myrrh does not have analgesic or anesthetic properties (Brown suggests that the anesthetic quality of the myrrh-wine offered to condemned persons was more due to the wine itself than the myrrh; Brown, Death, p. 941). The second drink, which Jesus accepts, is described as nothing more than sour wine (οξος), the vinegar-wine the soldiers had on hand for their own thirst (John specifically says that Jesus' drink was taken from a jar of wine already there). Why he drank it is not clear, but it sure wouldn't have knocked him unconscious.
But suppose that there was a successful conspiracy (perhaps involving Pilate or the centurion in charge of the crucifixion) to slip some narcotic into the sour wine, unbeknown to most of the observers, including the sources of the evangelists, who simply describe the drink as sour wine without knowing what it was really made of. We know that the Greeks and Romans, as well as other ancient peoples, were aware of the anesthetic effects of substances like mandrake, hemlock and henbane. Medical writers like Dioscorides as well as novelists like Apuleius recounted stories of potions given to people which sent them into a deep sleep. Did Roman medicine have at its disposal a substance which could safely have rendered Jesus unconscious, millenia before the advent of modern anesthesia?
The answer is an unqualified no. While historians believe that some ancient peoples experimented with anesthetics like the above, they also caution that "How far knowledge of the use of mandragora, opium or alchohol was applied for the relief of pain of surgery in classical times can never be known with certainty." (The History of Anaesthesia, p.25) For one thing, just as there was folklore about supernatural creatures there was folklore about medical substances, and stories regarding the latter seemed to have been passed on uncritically from one writer to the next (Craig Keener notes that Apuleius' novel Metamorphoses is "full of magic herbs that can do almost anything"; Keener, The Gospel of John: A Commentary, Vol.2, p.1180). Therefore we have no idea how effective infusions of mandragora really were in alleviating the pain of surgery. But we have reason to think that they were not very effective, as complaints about the pains of surgery and admiration of doctors who could operate as quickly as possible persisted well into the modern period.
The biggest problem, however, was that it was impossible without modern distillation and measurement techniques to control the dosage. This meant that its application was very dangerous. As Keith Sykes and John Bunker note, "a drug powerful enough to produce unconsciousness could just as easily produce death." (Anesthesia and the Practice of Medicine, p.6) This concern is born about by a description of the effects of mandragora's active ingredients (mostly hyocyamine and hyocine): "Small doses decrease and larger doses increase the heart rate. Larger doses may also cause drowsiness, arrhythmias, muscle paralysis, restlessness, fatigue, confusion, giddiness, hallucinations, delirium, dilated pupils, skin flushing and can easily cause death by respiratory paralysis." (Frederick Zugibe, The Crucifixion of Jesus: A Forensic Inquiry, p.160; cf. also The History of Anaesthesia, p.39) These effects are the last thing Jesus, in his heavily traumatized state on the cross, would want in order to have a chance of surviving his ordeal!
We should also note that the ancient literary references to narcotics all involve an infusion being given to a patient before surgery-in order to induce sleep or at least numb the pain-and their effectiveness was dependent on the delicacy and speed of the surgeon. But the drugged drink would have been given to Jesus after he had already been hanging on the cross for several hours, intense neuralgic pain shooting through his limbs from the nails in his hands and feet, open wounds from the scourging festering on his back, opening up every time he tried to breathe, grating against the wood of the cross. If anesthetics were already only of limited effectiveness when the patient was treated with the utmost care and speed, they couldn't possibly have had any effect on a person already in excruciating pain. The comments of Dr. Frederick Zugibe, forensic pathologist, are apropos:
In view of these facts, the question must be asked, "Would a preparation of mandrake given to Jesus on the cross be capable of rendering Jesus unconscious so that everyone would believe he was dead?" The answer is "not on your life." Jesus suffered some of the worst pains ever experienced by man. The hyocine and hyocyamine in the mandrake wouldn't touch this degree of pain, particularly with the weight of the body still on the nails. The amount and degree of pain would have rendered Jesus' body immune to the sedative effects of the mandrake. High doses of the mandrake preparation would have nullified the sedative effects, increased the degree of restlessness and confusion, and could easily have been lethal considering the degree of shock Jesus was experiencing...It is my opinion that if mandrake had been given to Jesus, instead of alleviating his pains and/or placing him into a coma or deep sleep, it would have hastened his death.
(The Crucifixion of Jesus, pp.160-161)
So we conclude that it is highly unlikely, even impossible, that Jesus could have survived the crucifixion by being given some anesthetic potion that made it appear he was dead. The sources say that the drink Jesus finally accepted was nothing more than common vinegar-wine, and if there could have been a successful conspiracy to give Jesus a narcotic there were no drugs available to Roman medicine that could have safely rendered Jesus unconscious.