Learn Russian: Мы не можем не замечать их трусость и безразличие. - We cannot help but notice their cowardice and indifference.

In Russian, using не with a conjugated form of мочь (like можем), followed by another не and an infinitive, expresses strong affirmation or inevitability. Literally, it means "we cannot not notice," which translates naturally to the English idiom "we cannot help but notice."

Why is the imperfective verb замечать used here instead of the perfective заметить?

The imperfective замечать is used because the noticing in this context is an ongoing, continuous reality rather than a single, completed event. The speaker is expressing that they are constantly observing this behavior over time.

What case are трусость and безразличие in, and why didn't their endings change?

They are both in the accusative case because they are the direct objects of замечать. Трусость is an inanimate feminine noun ending in a soft sign (3rd declension), and безразличие is an inanimate neuter noun. For both of these groups, the accusative form is identical to the nominative form.

How is the abstract noun трусость formed?

It is formed from the root noun трус (coward) using the suffix -ость. This suffix is extremely common in Russian for creating abstract feminine nouns from adjectives or other nouns, much like "-ness" or "-ice" in English.