Final answer:
The 'no false lemmas' concept by Gilbert Harman aims to address the Gettier problems by requiring that knowledge not be inferred from any false premises or steps in reasoning. This condition is meant to ensure that true beliefs are appropriately connected to the evidence used to arrive at them and are not based on luck or falsehoods.
Step-by-step explanation:
The concept of 'no false lemmas' is introduced by philosopher Gilbert Harman as an additional condition to the traditional Justified True Belief (JTB) account of knowledge, in an attempt to overcome cases like the Gettier problems. These problems show that having a justified true belief does not necessarily equal knowledge especially when based on erroneous or misleading information. A false lemma is essentially a false premise or step in the reasoning process. Harman's modification asserts that for someone to truly know a proposition, their belief must not be inferred from any falsehoods.
For example, Russell's man believes he knows the time because the stopped clock coincidentally shows the correct time. However, his belief in the time being correct relies on the false premise that the clock is working. Harman's 'no false lemmas' condition would dictate that since the man's belief was based on a falsehood (the working condition of the clock), it cannot count as knowledge, even though the belief is accidentally true.
Similarly, the concept of 'no defeaters' addresses situations where a person's justification can be undermined by additional information or 'defeaters'. The belief can only be regarded as knowledge if there aren't any existing defeaters that, if known, would undercut the justification for holding that belief.