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Exegesis: The Sensorites

By Richard Scheib and Michael Chisnall

The TARDIS materialises aboard a spaceship in orbit around the Sense-Sphere, where the native Sensorites have trapped the crew in suspended animation and others in a permanent state of fear. Susan finds that she has mental powers that enable her to communicate with and find back against the Sensorites who are equally frightened of humans after a previous expedition landed and gave the Sensorites much cause for alarm when they discovered large deposits of molybdenum on the planet which they want to mine. Also in the aftermath of the expedition something has been killing off the Sensorite population. The Doctor befriends them and makes an expedition into the city aqueducts to find the deadly nightshade that is poisoning the city water supply, placed there by the crazed survivors of the first expedition, fighting a lone war against the Sensorites. However in their absence the City Administrator, afraid of the human intent has replaced and taken over from the First Elder in order to wipe the humans out.


The Doctor: We are told that he is habitually obsessed with accumulating all pieces of information. We are also told that beneath his hard shell he is caring and compassionate. The person he cares for most is Susan. Up until this point he has never had any arguments with her, she seems very much under his thrall. Claims to have known Beau Brummel.

Susan: We learn here that she is a latent telepath. She seems somewhat surprised by this, which is a little surprising because Time Lords have a number of ESP talents. Perhaps all Time Lords do not have these? The Doctor seems to make the point that it is in some way related to the Sense-Sphere that she found the power. In the Doctor Who universe mental communication seems to run on frequencies (The Pirate Planet) - perhaps she is only sensitive to a certain band of broadcast frequencies upon which the Sensorites operate.


The Sensorites seem able to burn out the lock. In other stories this is seen to be all but totally invulnerable. The Sensorites seem to have only an average tech-level, the Doctor clearly admitting that TARDIS technology is well beyond theirs so I would suggest that the TARDIS lock is only another of their mental projections. The Doctor says, though, that they can't break the door down or this would disturb the field dimensions inside. It is difficult to see how he could break into the TARDIS considering its invulnerability. It is also difficult to see what could be meant by breaking the field dimensions as breaking the door wouldn't be overly different from what happens every time they open the door ordinarily.

The Sense Sphere - Planetary Readout

This exists somewhere on the outermost reaches of the galaxy. Said to be a normal planet and with a normal sun. It is a moonless world. Its colouration from space appears a bright yellow. Deserts, which are mentioned, would cause a dull yellow, which is the most likely option. Although from the city the mountains are observed to be of a yellow rock. The world is said to be quite abundant in lakes and forests, and obviously needing temperate zones to grow fruit, which would go against the notion of a desert-world and need some bodies of water at least. It is conceivable that these could be grouped around in fairly lush, temperate polar regions. If the ship is held in geostationary orbit then there could a single large continental mass of desert which fills the whole of vision which need not be representative of the rest of the planet. A more viable explanation would probably be that there are large deposits of sulphur or pyrite on the world. Molybdenum contains much sulphur, which we are told the planet is rich in. There is the possibility that this could be natural yellow-coloured flora, although this wouldn't account for yellow mountains. The land mass is reported to be larger than normal. It has a rather thin atmosphere only 19 miles in height, although this is at best a fairly tenuous - atmosphere doesn't really have a height, just a point where it thins out: on Earth 50% of the atmosphere is beneath 31/2 miles, 99% under 70 miles, but even the space shuttle being able to encounter atmosphere hundreds of miles up. More likely the 19 miles refers to the point where the ship begins to encounter re-entry. Even taking into account the size of the ship take less atmospheric buffeting than the ones we use, the atmosphere would only be about a half to a third the height of Earth's. As the Doctor and companions do not reportedly experience any discomfort in breathing or with pressure then yhe ground environment can't be far removed from Earth. The only way in which an Earth-like atmosphere could have such a reduced height by the increase of the average molecular mass. Earth atmosphere consists of nitrogen (78%), oxygen (20%), Argon (1%), Other - CO2, pollutants etc. (1%). All of these are about the same molecular weight so changing the proportions would have no effect. What is needed is some gas heavier than all of these, and the only gas heavy enough would be the inert gas Xenon. Even so it would have to a fairly major constituent to have any significant effect, roughly about a third of the atmosphere. Minerally the planet is rich in molybdenum. The trees on the Sense-Sphere have leaves that are phosphorescent in the dark.

The Sensorites

Biology: Described physically as having bulbous, bone-white heads, an enlarged cranium tapering down to a small V-shaped chin which is covered by snow-white whiskers which grow to up above the ears. The ears are cat-like and covered by a fibrous membrane. The eyes are described as disquieting - small, dark and lidless, betraying no emotion (or probably expression). The eyes are surrounded by prominent cheekbones which give an Oriental inscrutability and aged, wizened appearance. There is a bony protuberance in the middle of the face which is supposedly a nose, which evolution has apparently decided is no longer necessary. (Why?) There is a small, twitching mouth below the beard. Do they have moustaches? They are just over five feet in height. Their feet are circular pads, eighteen inches in diameter. Despite the clumsiness one would assume they move with feline grace and no sound. One must assume that have quite a wider pelvis than the human in order that they don't end up stepping on the other pad. The average dinner-plate is 10-12 inches across - try walking with one of those attached to your feet. Long-fingered hands. Husky, soft, almost whispering voices. All Sensorites are also physically identical - one must assume here that they have a DNA that allows for little or no variation in physical characteristics. They can't even tell one another apart. One would think that random determining factors - scars, genetic mishaps - birthmarks etc - could be though. Also the First Elder is elected to his job because of his great brain, which would seem to indicate that there is some differences in this area, although I don't really see how the size of brain had any relation to individual abilities. Perhaps what we merely have here is the common confusion of the brain with the mind.

The pupils of Sensorite eyes are naturally adjusted to receive as much light as possible, they have no eyelids. The Doctor and others do not find the Sense-Sphere sun to be unnaturally bright, so this would not appear to be an evolutionary adjustment. The Sensorites are unable to handle darkness. How do they handle night-time on their world, for instance? The phosphorescent trees are mentioned. What could be the case is that the Sense-Sphere has less of an ozone filtration layer than Earth, and that the Sensorites are used to seeing more into the natural ultra-violet spectrum, hence the Sense-Sphere's sun could be just the same as normal. The only other problem could be that the Doctor and companions might be getting rather more than expected suntans while on the planet. The problems with dark seem to be just as much psychological. How, one wonders, did they manage to dig the tunnels? And why can't they use the same means to go and look for the deadly nightshade? The lack of eyelids would also pose somewhat of a problem in keeping dust out if the eyes. Perhaps a regular, continuous flow of lachrymal fluid over the eyes? Perhaps part of the brain automatically, continually repels by psychokinetic means? We close our eyes at night to tune out our senses in order to sleep - how do the Sensorites cope? Perhaps, with the phosphorescent flora, they are used to constant visual stimuli. This may relate to their fear of darkness. Sensorites also have very sensitive hearing, perhaps a function of low atmospheric pressure. Extreme sound will stun the brain and paralyse the nerves - it will to us too - but the Sensorites have a much lower threshold. Sensorites are very biologically similar to humans (as the Doctor is able to measure the same symptoms of atropine poisoning for humans as Sensorites), possibly a common evolutionary stock, having a very similar diet. They are weaker and have a lighter build than humans - the possibility of lighter atmospheric pressure. All things considered the Sensorites are a weak and somewhat inefficient race - a wonder they survived evolutionarily - their feet would go against them being able to run well, making them poor predators, for instance. Perhaps this is a world that has a low number of natural predators, making survival fairly easy?

Sociological: The Sensorites are by nature a timid people, being scared by the Doctor's display of dominance and raised voice, also a very neurotic and afraid people - beside their ordinary problems with darkness, it seems to turn them into a state of utter helplessness, probably they are deadly afraid of enclosed, dark spaces, or else why didn't they go exploring the caverns with torches? The city appears to contain the whole of the Sensorite population. It is a domed city, full of crystalline towers, numbers of secluded gardens - it seems to be built for aesthetic value. The highest building of the city is the palace, containing at its apex a brilliant blue crystal dome, containing the council chambers (For some reason the palace also appears to contain a laboratory and house the Sensorite disintegrator cannon, used solely as an excavating machine). The one area in which Sensorite architecture doesn't do so well is in building a decent water purification system.

The Sensorites wear different sashes to denote the difference between them - the first Elder (the planetary ruler) two black sashes, the second Elder two, the Administrator (the city internal Administrator) a black band around his neck, the scientists vertical black bands with spiral designs. The Sensorite nation is divided up into a caste system which consists of the Elders - the thinkers and rulers; the Warriors (a rather odd function to have a whole caste devoted to considering their pacifist claims, perhaps this a redundant function or perhaps it is group which hunts animals for food); and the Sensorites - the common workers and servants to the Elders. It is a rigid system with strict codes of conduct - the Doctor for example being forbidden to speak to a lower class, the communication having to go through an Elder. A fatalistic philosophy seems to dominate the idea of this system, that one is born where they belong and to what they are best fitted to do as well as a passive emotional acceptance of facts no matter how bad they might seem. This thinking may seem odd for a race that is physically identical.

As even they are not able to tell themselves apart the society would seem to have major problems in telling who's who, the badges of office having been created to this extent. What about natural physical differences between male and female? We never do meet any Sensorite females, they must exist as all the Sensorites we meet are referred to as he. In all likelihood they hold a very subservient position in Sensorite society. The Sensorites are also a race very emotionally distant from each other. They have a strange view of their own psychology - that their own behavioural responses exist in different compartments of the brain, fear and alarm for instance (by alarm I think they mean reactive response to fear) and that they are able to simply lower their emotions once they have finished with emotion (they finding it quite hard to believe that John would become catatonic i.e. unable to cut off responding to his fear once the stimulus has been removed), the implication here being that they can shuttle about and clamp down on their emotions and reflexive responses at ease, which could be quite useful for things like preventing hysteria and allowing calm reason to guide one's actions at all times, the flip side of this being that it would make them a very stoic race, obviously explaining the distance in their emotional intercourse. This doesn't quite tie in with their fear of the dark though. Such has not always been the case, as we are told that they had a very war-like past. They are not entirely unfeeling and do prize sympathy and compassion (although care for others is said to be alien to their way of thinking), and do consider the willingness to risk one's life very honourable, but displays of affection and friendship are thought to be ostentatious. They do have family groups - although again there is the problem of telling who is who, perhaps they are able to tell one's close to them by small behavioural differences or by psychic means (although we never see the rackets in use in everyday Sensorite society, and I would tend to think these are specialised items with usage probably limited to the Elders). They claim their society is based on trust, that nobody wants anything and that all are content and that any anti-social urges are a flat impossibility. This is in all likelihood naiveté, as one such attempt does emerge within the story, it albeit something quite shocking to their thinking. And, despite their lack of belief in crime, they still manage to have an execution system. I find it hard to believe that people could live happily in such a caste system, but such would seem to be the case, possibly the belief that such is their destiny helping such. They think humans are naive - that a person lives while they have purpose, probably an out-growth of their belief in destiny of the caste system.

Parapsychological Profile: The Sensorites are naturally weak thought-broadcasters (but probably not thought readers) but with the aid of a small hand-held, ivory, tennis-racket shaped device are able to amplify these powers immensely. This amplifier seems to work along the electro-magnetic spectrum, causing radio interference when in operation. It is possible that the interference is caused by poor shielding of the instrument, possibly to improve the compactness of the instrument, although this is unlikely to do so by much. They are able to control human minds through the fear they are able to generate, increasing the mind's horrors a hundredfold. Emotions confuse the mind and leave it open to their influence. Displays of strong will power and fearlessness drive them away. One wonders why Ian and Barbara were not effected along with the rest of the humans aboard the ship? When in use the Sensorites demonstrate an ability to meld minds into one, their bodies moving in perfect unison. When Susan makes contact with them she says she hears hundreds of voices in her head. This is odd, as the Sensorites do not appear to be a gestalt anywhere else. I would suggest that this is an artificial condition that the racket is able to create that the other voices could be those of the Sensorite controllers on the planet monitoring the proceedings. It doesn't appear to be overly strong a gestalt though, for some reason, as when Barbara and Susan combine their resistance they are able to shake the control of the united minds and send both of the Sensorites into uncontrollable spasms. What might be happening here is that the Sensorites, being a people rather detached from interpersonal contact, may be being reticent in their sharing of minds, hence making the contact uneasy, easily able to be shaken by resistance where they are expecting none. These could even be trainees at this type of job, which might account for the severity of response. The racket is also able to project the Sensorite physically into space at incredible speeds, presumably creating an air bubble around him which would also siphon off minor problems like temperatures in space (a bubble of heated air), ultra-violet radiation (some type of shielding effect) and of inertia (probably psycho-kinetically). They also have remote control over the ship's controls, although it is unsure whether this is extra-sensory or electronic. The Doctor knows that the name of the planet is the Sense-Sphere without even having been told - perhaps the influence of the Sensorites leaves some vestigial traces of their presence. (Or perhaps this is just part of his amazing memory and ability to identify a planet at a glance, as demonstrated in The Pirate Planet and The Power of Kroll) How also do the Sensorites learn to speak English - the crew aboard the ship aren't using Babel fish, unless humanity managed to find a source of it on some planet - so the Sensorites must have learned it from the first expedition. The Sensorites also practice psychic healing of mental illness, this again with the aid of a electronically amplified process.

Technology: There is the racket, which seems an all-purpose device aiding in everything from telepathic amplification to providing space-travel and operating as an electronic burglar's tool. Their technology is very advanced, beyond Earth's at that point (although I would find that debatable, with the exception of the racket, Sensorite science being rather average). The one area in which they are very poor off scientifically is chemistry. They have limited space travel - about the same as Earth present, the ship's power system is unknown to them which may suggest an unfamiliarity with hyperspace technology. Have disintegrator weaponry (although this is a heritage from their war-like past, even if they do keep it in working order and claimed to used it in civil engineering, the minor incongruity here is that the Chief Scientist calls it his crowning glory i.e. it is his invention, which would make this war-like past in rather more recent memory than suggested or the Scientist somewhat older than one would think. Perhaps he means 'crowning glory' in the sense of an archaeological find or work of restoration), computer technology. One of the more interesting items is a machine that allows that purely physically obtained restoration of John's catatonic mind. The machine is even able to turn John's hair, which has turned white in fright, back to its natural colour.

Earth 28th Century

London on Earth has been rebuilt, now known as Central City, in the 24th Century. It is implied that humanity discovered hyperspace travel in the 21st Century. This is a century out with where I would place it on the chart of Earth future history. Before this space travel consisted of long voyages with cryogenic suspension.

The Expedition

The survey ship is a fifth of a mile in length. It has been speckled by thousands of meteorite showers in its four-year journey. The natural occurrence of meteorites in space is fairly rare and the likelihood of a ship being unable to spot them and stop running into them even less, so one could possibly conclude that part of the ship's mission has been to chart meteorite storms. Perhaps it may have been fuel cost effective not to avoid them. Possibly also this is a very old ship. But why didn't they use their deflection beams to avoid being struck? The ship seems to be devoid of any colour or decoration, purely functional - it seems unusual that its crew hasn't taken any steps to humanise their environment during their lengthy voyage. Instead of retro-rockets the ship has deflection beams, although it is difficult to see what they would act against in slowing velocity. The molybdenum is needed, having become the most valuable mineral in the galaxy, because of its 2622 degree melting point of vital necessity in hyperspace travel. The expedition is financed by a company called Interstellar Navigation, Exploration and Research.

This item appeared in TSV 11 (January 1989).

Index nodes: Exegesis, The Sensorites