Introduction to Systems Thinking — What is a System?
On this page 6 headings
Start here Kill all the snakes in a forest because “snakes are bad”. Soon there are too many rats, the rats eat all the grass, and the forest suffers. One small change, one big mess. Systems thinking teaches you to ask “What else will this affect?” before you act.
This week is taught by Prof. Shiva Subramaniam, with Prof. Prasanna, Prof. Sivakumar, Lt Col Jayakumar and Prof. Kartic sharing habits.
Why learn it? We often feel upset because we don’t understand why things happen, or why people behave the way they do. Systems thinking helps you understand the world. Prof. Shiva says the TCS leader F. C. Kohli told him in 1993 to learn it. He ignored that advice for years, and now regrets it.
The definition
A system is an interconnected set of elements that is coherently organised in a way that achieves something (a purpose).
Every system has three parts:
| Part | Meaning | Example: the digestive system |
|---|---|---|
| Elements | The parts | Mouth, tongue, oesophagus, stomach, liver, intestines… |
| Interconnections | How the parts link and depend on each other | Food passes from the mouth to the stomach to the intestines |
| Function / purpose | What the system achieves | To digest food |
Systems inside systems: the human body has the digestive, nervous and circulatory systems. Each one interacts with the others to keep you alive.
A heap vs a system
| Heap (not a system) | House (a system) |
|---|---|
| A pile of 100 stones | Walls, doors, windows, roof, foundation, all connected |
| Remove one stone: still a heap, just 99 stones | Remove the foundation or a wall: the house collapses |
| Not affected when one part is removed | Affected when one element is removed |
Easy test: If removing one part changes the whole thing, it’s a system.
What is systems thinking?
Systems thinking is a holistic approach to understanding:
- how the elements of a system are connected to each other,
- how the system relates to larger systems, and
- how a change in one part affects the rest.
Lecture example — the food chain In a jungle, the hawk, snake, bird, grasshopper, grass, mouse, owl, rabbit and fox are all connected. Remove the snakes, and the rats multiply and destroy the grass. Animals that depend on the grass suffer too. One missing element affects the whole system. Many climate problems happen because we remove elements without asking, “What will happen if I do this?”
What can you use it for?
- Examining problems in your family, campus or life
- Understanding situations and people
- Diagnosing what is really wrong
Lecture example — the doctor Even for a headache, a good doctor checks your blood pressure and weight, and asks about your sleep, food and exercise. Why? Everything is connected: Less walking → higher blood sugar → higher blood pressure → faster heart rate → more anxiety → even higher blood pressure. So the doctor treats the whole system, not just one part.
The six blind men and the elephant
Six blindfolded men each touch a different part of an elephant:
| Part touched | What they guessed |
|---|---|
| Tail | A rope or snake |
| Body | A wall |
| Ear | A fan |
| Leg | A pillar or tree |
| Trunk | A snake |
| Tusk | A spear |
Take off the blindfolds, and they see an elephant.
Lesson: The whole is not just the sum of its parts. In life, we often see only one small part and jump to conclusions. Look at how the parts connect before you decide.
In one line: A system is elements + interconnections + purpose; systems thinking looks at how parts connect, how systems link to bigger systems, and how one change affects everything. Exam words: system, elements, interconnections, purpose, heap vs system, systems thinking, holistic approach, food chain, interdependence, the whole is not the sum of its parts.