理所当然 taken for granted
Explanation
指事情合乎情理，应该如此。
It means that something is reasonable and natural.
Origin Story
从前，在一个小山村里，住着一位勤劳善良的老农。老农一生辛勤耕作，靠着双手养活一家老小。他有两个儿子，大儿子好吃懒做，整日游手好闲，小儿子则勤奋好学，非常孝顺。有一天，老农病倒了，两个儿子都守在床前，细心照料。老农渐渐康复，心里非常欣慰。他看着两个儿子，心里充满了感慨。大儿子理所当然地认为自己应该继承家业，而小儿子则默默地为父亲做着一切，不求任何回报。老农深知，小儿子才是真正值得托付的人。他把家业传给了小儿子，大儿子不服气，但老农解释道："勤劳和孝顺是理所当然应该受到回报的，而懒惰和不孝则理所当然应该受到惩罚。"大儿子听了父亲的话，羞愧难当，从此痛改前非，努力工作，最终也获得了成功。
Once upon a time, in a small mountain village, there lived a hardworking and kind old farmer. The farmer worked hard all his life, supporting his family with his own hands. He had two sons: the elder son was lazy and spent his days idling, while the younger son was diligent and very filial. One day, the old farmer fell ill, and both sons stayed by his bedside, carefully caring for him. The old farmer gradually recovered and was very pleased. He looked at his two sons and felt deeply moved. The elder son took it for granted that he should inherit the family business, while the younger son silently did everything for his father without asking for any reward. The old farmer knew that the younger son was the one to whom he could truly entrust his legacy. He passed the family business on to the younger son. The elder son was dissatisfied, but the old farmer explained: "Diligence and filial piety are naturally rewarded, while laziness and unfilial piety are naturally punished." The elder son was ashamed and changed his ways completely. He worked hard and eventually achieved success.
Usage
表示事情合情合理，理应如此。常用于表达一种必然性或客观事实。
It is used to express that something is reasonable and should be so. It is often used to express a necessity or objective fact.
Examples
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他理所当然地认为自己会赢。
tā lǐ suǒ dāng rán de rènwéi zìjǐ huì yíng
He took it for granted that he would win.
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她理所当然地继承了家业。
tā lǐ suǒ dāng rán de jìchéng le jiāyè
She inherited the family business as a matter of course.
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他理所当然地认为我会帮他。
tā lǐ suǒ dāng rán de rènwéi wǒ huì bāng tā
He took it for granted that I would help him.