Until relatively recently I was not aware of the difference between “consist of” and “consist in”. This is probably because among native English speakers “consist in” is very infrequently used in comparison to “consist of”, which is relatively common. In fact it wasn’t until I moved to Poland that I learned the difference.

Here it is:

• “consist of” – to have as its component parts or elements, i.e. the whole consists of its parts
• “consist in” – to have as its essential features, i.e. the whole is defined by its parts

Here are some examples of usage:

• The book consists of 50 chapters.
• The activity carried out at the plant consists of precision cutting, lathe work and heat moulding.
• The problem consists in  his failure to cooperate.
• The defence consists in  discrediting the claimant.

It’s no accident that I only learned the difference between the two phrases in Poland. In Polish the difference is made clear by two very different phrases – and as a result Poles are far better at explaining the difference than English people:

składać się z = consist of (literally “to be made up of”)

polegać na = consist in (literally “to rely on”)

Be aware that these days “consist in” is rarely seen in English writing outside of dusty philosophical texts. To many people it can sound strange or old fashioned, or simply wrong.