- It's a case of impermissible deception: the government is asking us to bring it about that burglars believe a falsehood, viz. that we are in when we aren't, and it's always wrong to bring it about that someone believe a falsehood (at least if the person does not consent).
- It's a case of permissible deception: the government is asking us to bring it about that burglars believe a falsehood, but the burglars have no right to know the truth here, so their rights are not violated if we bring it about that they believe a falsehood. (A similar argument was used to justify Sven-Goran Eriksson's lying to his employers about his sex life.)
- It's not a case of deception: we do not intend to bring it about that burglars believe a falsehood, we intend to bring it about that they do not believe the truth (viz. that we are out) -- our intentions would be fulfilled if the burglar suspended judgment. We intend merely that the lights' being on should bring it about that the burglar not think that we are in.
Another interesting example is a friend of a friend that used to smuggle Chinese Bibles into China. He was asked by a custom officer whether he had any literature in his case. He replied:
I have no literature that I can read.He said this because he thought it would be morally wrong to say 'No', as that would have been a lie. He also thought that it would have been foolish to say 'Yes', as then the custom officer would have found and confiscated the Bibles. He seemed quite pleased with the way round the impasse that he discovered (being unable to read Chinese). But if he wished to bring it about that the custom officer believe a falsehood (viz. that he had no literature in his case) is that really any better than lying? Obviously the custom officer's job was not to ascertain whether he had any literature that he could read but whether he had any literature at all in his case. But perhaps this friend of a friend intended merely that the custom officer shouldn't believe that he had any literature in his case; perhaps he intended just to confuse the officer.
One final, famous, example on the same point. In response to the famous case of the mad axeman at the door asking whether one's friend is inside, many mediaeval casuists asserted that one should say 'non est hic', which could mean either the true 'he is not eating here' or the false 'he is not here'. But if one intends that the axeman should take it in the latter sense, as surely one does, is one not attempting to deceive him, and is this not as bad as lying to him? (Again, perhaps it is possible that one is intending merely that he shouldn't form the opinion that the friend is inside; perhaps one is trying only to confuse, but this seems unlikely.)
Other examples of deception are:
(i) telling children 'noble' lies, e.g. about Santa Claus/Father Christmas;
(ii) teaching children simplified, and strictly false, versions of chemistry, physics, etc., because the truth is too hard for them to understand
(iii) giving approximations because the exact truth would be too tedious to spell out in detail.One can argue that (iii) doesn't really count because one is affirming not the approximation as an exact truth, but the approximation as an approximation, and this will be understood by one's interlocutor. Are (i) and (ii) justified, though?
Lastly, and most strikingly, there appear to be examples in the Bible where God himself deceives. The two most famous are 2 Thessalonians 2: 11, 'Therefore God sends them [the perishing] a strong delusion, so that they may believe what is false', and the story of God's sending the lying spirit to deceive Ahab, reported in 1 Kings 22:
19 Micaiah continued, "Therefore hear the word of the LORD : I saw the LORD sitting on his throne with all the host of heaven standing around him on his right and on his left. 20 And the LORD said, 'Who will entice Ahab into attacking Ramoth Gilead and going to his death there?'Is it significant that in these passages God acts through secondary means rather than directly affirming a falsehood himself. Do these passages show that it is permissible sometimes for us to deceive after all? Or do they show only that it is sometimes permissible for God to deceive?
"One suggested this, and another that. 21 Finally, a spirit came forward, stood before the LORD and said, 'I will entice him.'
22 " 'By what means?' the LORD asked.
" 'I will go out and be a lying spirit in the mouths of all his prophets,' he said.
" 'You will succeed in enticing him,' said the LORD. 'Go and do it.'
23 "So now the LORD has put a lying spirit in the mouths of all these prophets of yours. The LORD has decreed disaster for you."