As like as chalk and cheese.

Understand the thought

Meaning in plain English

Two things may be very different despite being put together in a comparison. Chalk and cheese give the difference a vivid form, encouraging attention to relevant distinctions without deciding that comparison is always useless.

What the words are saying

As like as introduces an expectation of resemblance, then chalk and cheese frustrates it. The expression is an ironic way to say that the two subjects differ markedly. In practical discussion, it may challenge a comparison that overlooks different purposes, circumstances or requirements. The saying itself does not identify which distinction matters, so a useful response names it rather than relying on the vivid phrase alone. Different things can still share a feature worth comparing. The point is to make the comparison appropriate to its purpose, not to dismiss an argument or a person without explaining why the apparent similarity is insufficient.

Everyday example

A team comparing two events distinguishes a small workshop from a public festival before deciding which staffing lessons can transfer between them.

When to use it

Use it when a comparison overlooks important differences between its subjects.

Agent-assisted editorial interpretation. This explains the words; it does not by itself verify their author or earliest origin.