science

Tertium comparationis

Tertium comparationis is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tertium comparationis rather than just read about it. In short: Tertium comparationis (Latin for "the third [part] of the comparison") is the quality that two things which are being compared have in common. It is the point of comparison which prompted the author of the comparison in question to liken someone or something to someone or something else in the first place.

Key takeaways

Tertium comparationis belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tertium comparationis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tertium comparationis from memory before moving on to harder problems.

Reference excerpt

Tertium comparationis (Latin for "the third [part] of the comparison") is the quality that two things which are being compared have in common. It is the point of comparison which prompted the author of the comparison in question to liken someone or something to someone or something else in the first place. If a comparison visualizes an action, state, quality, object, or a person by means of a parallel which is drawn to a different entity, the two things which are being compared do not necessarily have to be identical. However, they must possess at least one quality in common. This common quality has traditionally been referred to as tertium comparationis. The most common devices used to achieve this are metaphors and similes, especially, but by no means exclusively, in poetic language. In many cases one aspect of the comparison is implied rather than made explicit. The New Testament scholar Adolf Jülicher applied the concept of tertium comparationis to the parables of Jesus. According to Jülicher, a parable or similitude (extended simile or metaphor) has three parts: a picture part (Bildhälfte), a reality part (Sachhälfte), and the point of comparison (tertium comparationis) between the picture part and the reality part. "The kingdom of heaven is like treasure hidden in a field, which someone found and hid; then in his joy he goes and sells all that he has and buys that field" (Matthew 13:44). In this parable, the picture part is the hidden treasure, the reality part is God's kingdom, and the tertium comparationis is the inestimable value of the kingdom.

Examples Necessity is the mother of invention. (English proverb) Objects of comparison: relationship between mother and child, relationship between necessity and invention Tertium comparationis: source, where something derives from Woman is the nigger of the world. (John Lennon) Objects of comparison: treatment of Black people in US culture, treatment of women in global culture Tertium comparationis: inhumane treatment, subjugation, discrimination Goodbye, England's rose. (Elton John on the death of Diana, Princess of Wales) Objects of comparison: Diana; roses Tertium comparationis: beauty If they [our two souls] be two, they are two so As stiff twin compasses are two; Thy soul, the fixed foot, makes no show To move, but doth, if th'other do. (John Donne: "A Valediction: Forbidding Mourning") (Read the whole poem.) Objects of comparison: two souls; twin compasses Tertium comparationis: a non-physical link between separate objects that causes action in one to result in action to the other.

References

Worked examples

Example 1 — a first encounter with Tertium comparationis

Start with the simplest possible case. Write down what Tertium comparationis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tertium comparationis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tertium comparationis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tertium comparationis

In research: Tertium comparationis appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tertium comparationis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tertium comparationis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Rhetoric, Semantics, so understanding it makes those chapters shorter.
In everyday life: Look for Tertium comparationis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tertium comparationis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tertium comparationis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tertium comparationis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tertium comparationis in simple terms?

Why does Tertium comparationis matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tertium comparationis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tertium comparationis.