When we previously discussed the provenance of assets, we saw that the history of an asset was important—it provided confidence to participants in a network—and this increased trust. Likewise, transaction history is important, because it too increases trust. Why? Well, it comes back to those signatures. Any change must agreed by all the participants involved in the transaction, and the signatures in each transaction provide confidence that every counter-party consented to the exchange. A history of transactions is even better—it shows that all all points in time, every participant in the network has agreed with every change described by every transaction!

A blockchain history contains a sequenced order of transactions. Although, an order seems to imply that transactions occur in a time-defined sequence, this is only partially true. For example, if I pay money into my bank account at 11.00 a.m., and then make a payment from my bank account at 11.30 a.m., there is a very real sense in which the first transaction happened before the second.

Likewise, if you pay money into your bank account at 11.00 a.m., and then you make a payment at 11.30 a.m., there is a definite ordering of your transactions. However, let's now ask whether our 11.00 a.m. transactions happened before or after each other? Or, our 11.30 a.m. transactions? Does it matter whether my 11.00 a.m. transaction is recorded after your 11.30 a.m. transaction, even though it may have occurred, in some sense, before it?