The Unspeakables in the Thought division are put through gruelling mental tests to determine their stability and endurance before being accepted into the division because those employed within have been known to experiment on one another when a suitable test subject is lacking. The processes of the brain are the focus of the study here. How the mind absorbs, disseminates, understands and then stores information is of vital importance. How to keep the brain functioning without the rest of the body is also something the Unspeakables here have taken time to understand, and to successful result. Because of the practical approach often taken with examination and experimentation of the mind, Unspeakables entering this division are given training on magical dissection specialising in the brain.

Part of the Thought division of the Department of Mysteries is a large room which houses a seemingly endless number of shelves stocked with glass jars. These jars are filled with a green solution the Unspeakables concocted which helps to keep the brains swimming about inside fresh and functioning. These brains tend to be former test subjects of the Unspeakables whilst inside a proper body and have been kept for further experimentation. Given that many of their test subjects have historically been criminals and other unsavouries brought into the department by the NCOs these brains tend to be a bit feisty and rather cranky when disturbed, sometimes leading to attack.

Both Imperius and Cruciatus were developed in this division. Imperius was a result of the ongoing attempt to discover a way to properly control one's mind. The Unspeakables found, after months of tireless toil, that if one implanted the correct charm, in this case Imperio, that it could be controlled by another. This is not a fail-proof plan, however, as there are those with strong enough minds to break the charm once implanted. Studies are under way to develop both an unbreakable version of Imperius as well as to create charms which will give the caster control over specific things of their own choosing.

Cruciatus, however, was accidental. There was a small group of Unspeakables working on the ways in which feelings and thoughts could be implanted into one's mind. They discovered the mind's trigger for pain accidentally, which led to further experimentation. Eventually they came up with Cruciatus which works by forcing the brain to create the signals for pain which the rest of the body then accepts as fact. The curse is entirely an attack on one's mental capabilities as all pain truly is something that register's in one's mind when it receives the information from one's nerves. Cruciatus works in the opposite order of creating the information of pain in the mind and sending that information back down to the nerves to actually feel the pain.

Some of the things Unspeakables are studying in this division:
• The physiology of the brain
• The ways in which alterations to the physiology affect the mind's function
• Ways in which to control the mind through charms, curses and potions
• Partial mind control
• Targeting specific areas of the mind for alteration
• Time-lapsing temporary memory charms
• Irreversible memory charms
• The effects on the human mind when magical non-human brain matter is attached
• How to properly put a brain back together after it has been taken apart physically
• How to attach parts of different brains together and what the end product results in
• Implanting a brain after it has been removed from one's head and whether or not implanting it into a new body has any significant change to the mind's functions
• Alteration of thought patterns
• Alteration of information digestion
• Alteration of how the mind stores and retrieves information from long and short term memory
• The complete and irreversible obliteration of all memory
• Personality and how the mind constructs it
• The brain's connection to personality vs. the soul's connection to personality
• The soul's connection to the brain vs. the body.
• Altering the personality through physical changes to the brain
• Creating psychosis in the brain
• Potential cures of psychosis, both naturally developing and trauma-induced
• Hallucinations: how they manifest, how they can be removed or imposed and how to control them
• Degeneration of the mind once removed from its body
• Can the mind be regenerated?
• The effect of time travel on the mind
• How changes to the time line affect the mind.
• Emotional responses and how they can be altered, induced or eradicated
• World perception and how to cause permanent changes to vision interpretation
• Effective and unalterable means of desocialisation/resocialisation without memory charms.
• Mental conditioning
• Nature vs. Nurture and how the personality can be altered through the altering of memory

Department of Mysteries: Death | Love | Space | Thought | Time | Non-Official Cover Operatives