'I' before 'E' except after 'C'
or when sounded as 'A', as in 'neighbor' or 'weigh'.
Albeit, there's weird words like 'leisure' and 'neither'
('foreign' and 'counterfeit' don't make sense either).
'Seismic' and 'seisure' and 'protein' and 'height'...
...the rule is quite useless but possibly might
just yet be worth saving with some alteration:
(oops: 'heir', 'their', and 'sovereign'... 'decaffeination'...)
so yes it's quite simple, as I'm sure you can see:
     "'I' before 'E' when it wants to be!"

-- Daniel Reeves, 1999