Doing evil knowingly and unknowingly In the Milindapanha, Nagasena points out to king Milinda that doing evil knowingly accrues lesser demerit than doing evil unknowingly. Does the Buddha make the same statement anywhere in the Suttas?

The king asked: &quot;Venerable Nagasena, for whom is the greater demerit, one who knowingly does evil, or one who does evil unknowingly?&quot;
The elder replied: &quot;Indeed, your majesty, for him who does evil not knowing is the greater demerit.&quot;
&quot;In that case, venerable Nagasena, would we doubly punish one who is our prince or king's chief minister who not knowing does evil?&quot;
&quot;What do you think, your majesty, who would get burned more, one who knowing picks up a hot iron ball, ablaze and glowing, or one who not knowing picks it up?&quot;
&quot;Indeed, venerable sir, he who not knowing picks it up would get burned more.&quot;
&quot;Indeed, your majesty, in the same way the greater demerit is for him who does evil not knowing.&quot;
&quot;You are clever, venerable Nagasena.&quot;

Milindapanha - Access to Insight
My interpretation of this is not about unintended action vs intended action as one of the answers suggests. Instead I see it as comparing intended action with the view that the action is unwholesome vs intended action with the view that the action is wholesome. It's not about intending harm vs not intending harm, instead it's about intending harm knowing that causing harm is bad vs intending harm not knowing that causing harm is bad.
The source is Miln III,7,8 [84].

The other day, I happened to read a discussion of this passage in "Development in the Early Buddhist Concept of Kamma/Karma" by James Paul McDermott (page 113-114).

Based on what I have read, I do not believe that there is any specific quote in the Suttas / Vinaya that specifically supports this passage. The Suttas (AN 6.63) equate kamma with volition / intention and as McDermott explains, this was developed in the Abhidhamma (particularly the Kathāvatthu), further developed in Milindapañha and even further developed in the Abhidharmakośa. Of course, the commentaries developed the concept of kamma to a new level again (this was beyond the scope of McDermott's book).

One has to be careful with interpreting this parable of getting burned by the hot iron. The point is that a unskillful act done with wrong view will generate more weighty kamma... somebody who knows that the unskillful act is wrong will have less volition / intention when performing the unskillful act as compared to another person who sees absolutely nothing wrong with the unskillful act (i.e. accompanied by wrong view). 

@Jayarava, I have admired some of your writings / posts. Thanks for prompting me to look deeper at this passage (I love to learn). Here is the passage in Pāḷi:


  Rājā āha ‘‘bhante nāgasena, yo jānanto pāpakammaṃ karoti, yo ajānanto pāpakammaṃ karoti, kassa bahutaraṃ apuñña’’nti? Thero āha ‘‘yo kho, mahārāja, ajānanto pāpakammaṃ karoti, tassa bahutaraṃ apuñña’’nti. ‘‘Tena hi, bhante nāgasena, yo amhākaṃ rājaputto vā rājamahāmatto vā ajānanto pāpakammaṃ karoti, taṃ mayaṃ diguṇaṃ daṇḍemā’’ti? ‘‘Taṃ kiṃ maññasi, mahārāja, tattaṃ ayoguḷaṃ ādittaṃ sampajjalitaṃ sajotibhūtaṃ eko jānanto gaṇheyya, eko ajānanto gaṇheyya, katamo [kassa (ka.)] balavataraṃ ḍayheyyā’’ti. ‘‘Yo kho, bhante, ajānanto gaṇheyya, so [tassa (pī. ka.)] balavataraṃ ḍayheyyā’’ti. ‘‘Evameva kho, mahārāja, yo ajānanto pāpakammaṃ karoti, tassa bahutaraṃ apuñña’’nti.


I believe that the key word is "ajānanto". In the translation above, it is rendered as "unknowingly". T.W. Rhys Davids translates this as "inadvertently". Bhikkhu Pesala translates this as "unconsciously". PED uses translations such as "unaware" and "unsuspecting".

I do not think "ajānanto" is equivalent to "ignorance" (delusion / moha). "Ajānanto" seems to be closer to "unwise attention", not seeing things as they truly are. For this reason, I think wrong view is a better handling, even though "micchādiṭṭhi" is not used in the text. @Jayarava, your knowledge of Pāḷi is far superior to mine, so I would be very willing to be corrected. 

Oops, I just read your answer below, so let me add more...

I am an Abhidhamma teacher and this certainly colours my world view :-) Let me put an Abhidhamma spin on this to see if it helps. The Milindapañha was written after the Abhidhamma, so it is possible that in this passage, Nāgasena is attempting to clarify a doubt from the Abhidhamma.

Kamma comes from intention. The ethical quality of the kamma created comes from the roots (attachment / aversion / delusion for unwholesome, non-attachment / non-aversion / understanding for wholesome). 

I do not believe that this passage from the Milindapañha is talking about the ethical quality of the kamma created. 

I do believe that this passage from the Milindapañha is talking about the weightiness / intensity of the kamma created... and this is a different issue. The weightiness / intensity of the kamma created is a question of strength of volition.

In the case of unwholesome kamma-creating mental states, the strength of volition can depend on pleasant / neutral feeling (pleasant feeling contributes to stronger volition), prompted / spontaneous (spontaneous contributes to stronger volition) and associated / disassociated with wrong view (associated with wrong view contributes to stronger volition). I believe that this passage from the Milindapañha is talking about the third factor; "associated / disassociated with wrong view".