Difference between passive voice and causative-passive form

Question

I am confused with following question. What's the difference between たべられる and たべさせられる?

Answer 1

• 食べる "to eat (something)" (active voice)

• 食べられる "to be eaten (by someone)" (passive voice)

• 食べさせる "to make/let (someone) eat (something)" (active voice, causative)

As you might know, the passive voice can sometimes express a feeling of unhappiness towards the result of the action (that is done against one's will).

In this case, the one doing the action of the verb is always doing it against his will, forced by someone.

Hence, 食べさせられる means "to be forced (by someone) to eat (something)".

私はケーキを食べた。
I ate the cake.

ケーキは私に食べられた。
The cake has been eaten by me. ← Unnatural because of the inanimate subject

私は弟にケーキを食べさせた。
I made/let my little brother eat the cake.

私は兄にケーキを食べさせられた。
My big brother made me eat the cake. / I've been forced by my big brother to eat the cake.

私は友達に一時間も待たせられた。
I had to wait my friend for a good hour. / My friend made me wait a good hour.

For the Godan verbs, される is often used instead of せられる:

待つ → 待たせられる → 待たされる

Answer 2

Does this help to illustrate the difference?

• "Unfortunate"

  タコに食べられた。
  I was swallowed by an octopus.

• "Not so serious"

  タコを食べさせられた。
  Someone made me eat octopus.

• "Unlikely"

  タコに食べさせられた。
  An octopus (spoon-)fed me.