This will be a long one but here we go...
こと is a quite fascinating aspect of Japanese grammar that goes deeper than just meaning "about." To fully understand its usage, I think it's helpful to compare it with もの, as these two concepts often overlap but carry distinct semantic implications.
もの is used for universally perceivable or collectively agreed-upon things - matters that can be objectively felt or observed by everyone. For example:
- 負けるもんか - As if I'd lose!
- この料理は美味しいものだ - This dish is delicious -
In these cases, もの is used because these are feelings or states that anyone could perceive or understand - the frustration at being doubted, or the objective deliciousness of food.
こと, on the other hand, deals with personal, theoretical, or abstract concepts - things that exist in our minds or are subject to individual interpretation. For instance:
- 日本語を勉強することは難しい - The act/concept of studying Japanese is difficult
- 英語のことについてあんまり詳しくはない - I'm not very knowledgeable about English [as a concept/field]
- 将来のことを考えている - I'm thinking about the future [as an abstract concept]
This distinction becomes particularly important when we consider the Japanese cultural concept of 建前 (tatemae - the public face) versus 本音 (honne - the true feelings). When using のこと in expressions of feeling or emotion, it often signals that we're talking about someone's true nature or our personal perception of them, rather than their public persona.
Consider these variations:
- 田中さんが好きです (Tanaka-san is likeable) - A simple statement of liking
- 田中さんのことが好きです (Everything about Tanaka-san is likeable -> I love Tanaka-san) - A deeper, more personal appreciation of their true nature
This also explains why のこと appears in phrases like:
- うちでは父のことを「おやじさん」と言います (We call our father "Oyaji-san") - Referring to the entire concept of the father, not just the person he is to others
- 私のことは放っておいてよ (Leave me alone) - Referring to everything about the speaker, their whole situation (imagine this like a bubble)
When it comes to giving advice or stating general truths, ことだ and ものだ have distinct uses as well:
- 若いうちに勉強することだ (It's important to study while young) - Personal advice, suggesting what one should do (my perception or concept)
- 若いうちに勉強するものだ (Young people should study) - A general social expectation or universal truth
The ことだ form tends to be more direct advice for specific situations, while ものだ expresses broader societal norms or expectations that everyone generally accepts.
This is why in your original example, カノジョのことが大好き carries a deeper, more comprehensive meaning than just 彼女が大好き. It's expressing love not just for the girlfriend as a person, but for everything that makes her who she is - her true nature, characteristics, and essence.
