difficult to perceive

See: impalpable
References in classic literature ?
I answered all her little questions; she prolonged her talk, I went on following its many little windings; she sat so long, said so much, varied so often the topics of discourse, that it was not difficult to perceive she had a particular aim in thus detaining me.
These ladies were graceful and handsome; and it was not difficult to perceive at a glance that even their presence there, had a highly beneficial influence on the patients who were grouped about them.
Since the late 1990s, Mischel and Yuichi Shoda have developed an if-then model of person-by-situation interactions that reveals considerable stability and consistency at the level of individual personality structure, even if the underlying structure (like that of a musical piece) may be difficult to perceive in light of dynamic behavioral patterns (such as changing musical notes).
In many fields of technology, the value of fundamental, curiosity-driven research by inquiring scientists, not bent on any particular applications, is somewhat more difficult to perceive.
The perigree side is 50,000 closer than the apogee side of the moon's orbit although the difference can be difficult to perceive.
Of course Erdoy-an will continue to support the party when he ascends to the office in Ecankaya but at the same time, a separation, the true dimensions of which are difficult to perceive even now, will occur.
asserts that "it is difficult to perceive in the few rare trinitarian formulas of the New Testament a revelation of the God who is one and three.
As one investigates the painting close up, the landscape, the people, and other realistic elements that populate the painting may be difficult to perceive, as all of them seem like a perplexing, bewildering mixture of colors.
It is difficult to perceive the fear and distress this caused the woman.
While it is difficult to perceive evidence of two hands at work in the surface of the Malvagna Triptych, infrared reflectograms of the underdrawing do lend credence to Ainsworth's remarkable thesis.
Unless this structure is fundamentally amended it is difficult to perceive a universal commitment to meet the targets of the climate summit.
Consequently, it is not too difficult to perceive the ongoing trial as a disingenuous attempt to vilify and nullify the various contributions of the parties to the CPA and the successful implementation of the processes, up to and including, the historic election and inauguration of the continent's first female elected president.