Technical means do not allow detection of alien life
Our current technology does not allow detection of an alien life.
<
(2 of 2)
Context
With current technology we can only prove if a planet is in a habitable zone but not if it can actually harbour intelligent life.
The Argument
Possible method of detecting life on an exoplanet:
Detection of a sign of life on a planet (such as river, cities, artifacts) requires an image of planet: this would require an impractical optical resolution of a telescope positioned in the Solar System).
Sending a probe on an outer solar system is also highly impractical (length of travel).
Detection of signals form an alien life is impractical (see also SETI argument)