In English, we sometimes use adjectives as nouns to talk about abstract ideas, like "the good" or "the unknown". Portuguese does exactly the same thing, which is especially useful when discussing philosophy, ethics, or complex dilemmas.
Turning adjectives into abstract nouns
To transform an adjective into an abstract noun, place the masculine singular definite article o directly before the masculine singular form of the adjective. This translates to "the [adjective]" or "the [adjective] thing".
| The philosopher studies the good and the bad. | O filósofo estuda o bom e o mau. |
| Ethics separates the fair from the unfair. | A ética separa o justo do injusto. |
| In this dilemma, it is difficult to know the right thing. | Neste dilema, é difícil saber o certo. |
Notice how o bom means "the good", o injusto means "the unfair" (contracted with de to form do injusto), and o certo means "the right thing". The adjective always stays in its default masculine singular form.
Discussing philosophy and ethics
You can use this pattern with almost any adjective to distill complex situations down to their core concepts, such as "the absolute" (o absoluto), "the essential" (o essencial), or "the obvious" (o óbvio).
| Is morality the absolute or the relative? | A moral é o absoluto ou o relativo? |
| In an action, the essential thing is the consequence. | Numa ação, o essencial é a consequência. |
| The philosopher explained the obvious again. | O filósofo voltou a explicar o óbvio. |
| Ethics studies the rational in the action. | A ética estuda o racional na ação. |
