If you have studied "mathematical logic", it may be easier to understand. For propositional logic that takes a single proposition as the research object (that is, regardless of the internal structure of the proposition), conjunctions (not, or, and, if … then ……, if and only if, etc. ) What is needed to construct compound propositions from atomic propositions can be converted to each other.

The two basic transformations used in this problem are:

(1) If p, then q; Equivalent to:

(not p) or q; -I hope you can understand the meaning of brackets;

(2)P and q; Equivalent to:

Not ((not p) or (not Q))；); );

To your question:

P and q;

Equivalent to:

Not ((not p) or (not Q))；); );

Equivalent to:

No (if P (not Q))；); );

If you don't understand, you can continue to analyze: Middle school mathematics has learned the concept of "negative proposition", so the above proposition is equivalent to:

No (if q is (not P))；); );

This shows that P and Q have the same status; This is the same as "and".

If you still don't understand, you can give a practical example:

I like studying and working.

(1) is first converted to the form in parentheses:

If I love learning, then I don't love work;

Or:

If I love labor, then I don't like learning;

These two sentences have the same meaning, both of which mean:

I only love one, study and work, or neither;

(2) Now if the word "no" outside the brackets is taken into account, it shows that the conclusion just now is completely wrong; Namely:

I don't love only one, nor do I "love neither"; And (only) is: both love;