Is the phrase "因为爱所以爱" a tautology?
tautology
the saying of the same thing twice in different words, generally considered to be a fault of style (e.g., they arrived one after the other in succession )

'one after the other' and 'in succession' are the same thing in different words , so one of them is redundant.
&quot;因为爱所以爱” or 为爱而爱 (to love because of love) follows a common phrase structure [因为 X 所以 Y] or simply [为 X 而 Y]
X is the reason; Y is the resulted action
For example:
In &quot;因为貪心所以殺人&quot; (Killing because of greed), 貪心 is the reason; 殺人 is the resulted action
In &quot;因为恐惧所以屈服&quot; (Yield because of fear), 恐惧 is the reason; 屈服 is the resulted action

In &quot;因为爱所以爱” (Love because of love), 爱 is the reason; 爱 is the resulted action

Notice, when the reason is the same as the resulted action, it means you do something because you wanted to do something with no other reason.
Example:
Killing for Killing's sake (为殺人而殺人)= You kill because you wanted to kill (因为想殺人而殺人)
Love for love's sake (为爱而爱)= You love because you wanted to love (因为想爱而爱)

To make &quot;因为爱所以爱” sound more nature, you can either not omit '想' and write &quot;因为想爱所以爱” (I love because I wanted to love) or replace '因为' with '為了' and write &quot;為了爱而爱&quot; or simply &quot;為爱而爱&quot; (love for love's sake)
The main point of the title &quot;因为爱所以爱” is  &quot;it doesn't need a reason to love&quot;

Since neither 爱 is redundant in this sentence, it is not tautology, just a flawed sentence